Release notesยถ
This page contains the release notes for PennyLane.
- orphan
Release 0.39.0 (current release)ยถ
New features since last release
Creating spin Hamiltonians on lattices ๐
Functionality for creating custom Hamiltonians on arbitrary lattices has been added. (#6226) (#6237)
Hamiltonians beyond the available boiler-plate ones in the
qml.spin
module can be created with the addition of three new functions:qml.spin.Lattice
: a new object for instantiating customized lattices via primitive translation vectors and unit cell parameters,qml.spin.generate_lattice
: a utility function for creating standardLattice
objects, including'chain'
,'square'
,'rectangle'
,'triangle'
,'honeycomb'
,'kagome'
,'lieb'
,'cubic'
,'bcc'
,'fcc'
, and'diamond'
,qml.spin.spin_hamiltonian
: generates a spinHamiltonian
object given aLattice
object with custom edges/nodes.
An example is shown below for a \(3 \times 3\) triangular lattice with open boundary conditions.
lattice = qml.spin.Lattice( n_cells=[3, 3], vectors=[[1, 0], [np.cos(np.pi/3), np.sin(np.pi/3)]], positions=[[0, 0]], boundary_condition=False )
We can validate this
lattice
againstqml.spin.generate_lattice('triangle', ...)
by checking thelattice_points
(the \((x, y)\) coordinates of all sites in the lattice):>>> lp = lattice.lattice_points >>> triangular_lattice = qml.spin.generate_lattice('triangle', n_cells=[3, 3]) >>> np.allclose(lp, triangular_lattice.lattice_points) True
The
edges
of theLattice
object are nearest-neighbour by default, where we can add edges by using itsadd_edge
method.Optionally, a
Lattice
object can have interactions and fields endowed to it by specifying values for itscustom_edges
andcustom_nodes
keyword arguments. The Hamiltonian can then be extracted with theqml.spin.spin_hamiltonian
function. An example is shown below for the transverse-field Ising model Hamiltonian on a \(3 \times 3\) triangular lattice. Note that thecustom_edges
andcustom_nodes
keyword arguments only need to be defined for one unit cell repetition.edges = [ (0, 1), (0, 3), (1, 3) ] lattice = qml.spin.Lattice( n_cells=[3, 3], vectors=[[1, 0], [np.cos(np.pi/3), np.sin(np.pi/3)]], positions=[[0, 0]], boundary_condition=False, custom_edges=[[edge, ("ZZ", -1.0)] for edge in edges], custom_nodes=[[i, ("X", -0.5)] for i in range(3*3)], )
>>> tfim_ham = qml.spin.transverse_ising('triangle', [3, 3], coupling=1.0, h=0.5) >>> tfim_ham == qml.spin.spin_hamiltonian(lattice=lattice) True
More industry-standard spin Hamiltonians have been added in the
qml.spin
module. (#6174) (#6201)Three new industry-standard spin Hamiltonians are now available with PennyLane v0.39:
qml.spin.emery
: the Emery modelqml.spin.haldane
: the Haldane modelqml.spin.kitaev
: the Kitaev model
These additions accompany
qml.spin.heisenberg
,qml.spin.transverse_ising
, andqml.spin.fermi_hubbard
, which were introduced in v0.38.
Calculating Polynomials ๐ข
Polynomial functions can now be easily encoded into quantum circuits with
qml.OutPoly
. (#6320)A new template called
qml.OutPoly
is available, which provides the ability to encode a polynomial function in a quantum circuit. Given a polynomial function \(f(x_1, x_2, \cdots, x_N)\),qml.OutPoly
requires:f
: a standard Python function that represents \(f(x_1, x_2, \cdots, x_N)\),input_registers
(\(\vert x_1 \rangle\), \(\vert x_2 \rangle\), โฆ, \(\vert x_N \rangle\)) : a list/tuple containingWires
objects that correspond to the embedded numeric values of \(x_1, x_2, \cdots, x_N\),output_wires
: the Wires for which the numeric value of \(f(x_1, x_2, \cdots, x_N)\) is stored.
Here is an example of using
qml.OutPoly
to calculate \(f(x_1, x_2) = 3x_1^2 - x_1x_2\) for \(f(1, 2) = 1\).wires = qml.registers({"x1": 1, "x2": 2, "output": 2}) def f(x1, x2): return 3 * x1 ** 2 - x1 * x2 @qml.qnode(qml.device("default.qubit", shots = 1)) def circuit(): # load values of x1 and x2 qml.BasisEmbedding(1, wires=wires["x1"]) qml.BasisEmbedding(2, wires=wires["x2"]) # apply the polynomial qml.OutPoly( f, input_registers = [wires["x1"], wires["x2"]], output_wires = wires["output"]) return qml.sample(wires=wires["output"])
>>> circuit() array([0, 1])
The result,
[0, 1]
, is the binary representation of \(1\). By default, the result is calculated modulo \(2^\text{len(output_wires)}\) but can be overridden with themod
keyword argument.
Readout Noise ๐
Readout errors can now be included in
qml.NoiseModel
andqml.add_noise
with the newqml.noise.meas_eq
function. (#6321)Measurement/readout errors can be specified in a similar fashion to regular gate noise in PennyLane: a newly added Boolean function called
qml.noise.meas_eq
that accepts a measurement function (e.g.,qml.expval
,qml.sample
, or any other function that can be returned from a QNode) that, when present in the QNode, inserts a noisy operation viaqml.noise.partial_wires
or a custom noise function. Readout noise in PennyLane also follows the insertion convention, where the specified noise is inserted before the measurement.Here is an example of adding
qml.PhaseFlip
noise to anyqml.expval
measurement:c0 = qml.noise.meas_eq(qml.expval) n0 = qml.noise.partial_wires(qml.PhaseFlip, 0.2)
To include this in a
qml.NoiseModel
, use itsmeas_map
keyword argument:# gate-based noise c1 = qml.noise.wires_in([0, 2]) n1 = qml.noise.partial_wires(qml.RY, -0.42) noise_model = qml.NoiseModel({c1: n1}, meas_map={c0: n0})
>>> noise_model NoiseModel({ WiresIn([0, 2]): RY(phi=-0.42) }, meas_map = { MeasEq(expval): PhaseFlip(p=0.2) })
qml.noise.meas_eq
can also be combined with other Boolean functions inqml.noise
via bitwise operators for more versatility.To add this
noise_model
to a circuit, use theqml.add_noise
transform as per usual. For example,@qml.qnode(qml.device("default.mixed", wires=3)) def circuit(): qml.RX(0.1967, wires=0) for i in range(3): qml.Hadamard(i) return qml.expval(qml.X(0) @ qml.X(1))
>>> noisy_circuit = qml.add_noise(circuit, noise_model) >>> print(qml.draw(noisy_circuit)()) 0: โโRX(0.20)โโRY(-0.42)โโโโโโโโHโโRY(-0.42)โโPhaseFlip(0.20)โโค โญ<X@X> 1: โโHโโโโโโโโโPhaseFlip(0.20)โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โฐ<X@X> 2: โโHโโโโโโโโโRY(-0.42)โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค >>> print(circuit(), noisy_circuit()) 0.9807168489852615 0.35305806563469433
User-friendly decompositions ๐
A new transform called
qml.transforms.decompose
has been added to better facilitate the custom decomposition of operators in PennyLane circuits. (#6334)Previous to the addition of
qml.transforms.decompose
, decomposing operators in PennyLane had to be done by specifying astopping_condition
inqml.device.preprocess.decompose
. Withqml.transforms.decompose
, the user-interface for specifying decompositions is much simpler and more versatile.Decomposing gates in a circuit can be done a few ways:
Specifying a
gate_set
comprising PennyLaneOperator
s to decompose into:from functools import partial dev = qml.device('default.qubit') allowed_gates = {qml.Toffoli, qml.RX, qml.RZ} @partial(qml.transforms.decompose, gate_set=allowed_gates) @qml.qnode(dev) def circuit(): qml.Hadamard(wires=[0]) qml.Toffoli(wires=[0, 1, 2]) return qml.expval(qml.Z(0))
>>> print(qml.draw(circuit)()) 0: โโRZ(1.57)โโRX(1.57)โโRZ(1.57)โโญโโโค <Z> 1: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค 2: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโฐXโโค
Specifying a
gate_set
that is defined by a rule (Boolean function). For example, one can specify an arbitrary gate set to decompose into, so long as the resulting gates only act on one or two qubits:@partial(qml.transforms.decompose, gate_set = lambda op: len(op.wires) <= 2) @qml.qnode(dev) def circuit(): qml.Toffoli(wires=[0, 1, 2]) return qml.expval(qml.Z(0))
>>> print(qml.draw(circuit)()) 0: โโโโโโโโโโโโญโโโโโโโโโโโโโญโโโโโโญโโโTโโโญโโโค <Z> 1: โโโโโญโโโโโโโโโโโโโญโโโโโโโโโโTโโฐXโโTโ โโฐXโโค 2: โโHโโฐXโโTโ โโฐXโโTโโฐXโโTโ โโฐXโโTโโHโโโโโโโโโค
Specifying a value for
max_expansion
. By default, decomposition occurs recursively until the desired gate set is reached, but this can be overridden to control the number of passes.phase = 1.0 target_wires = [0] unitary = qml.RX(phase, wires=0).matrix() n_estimation_wires = 1 estimation_wires = range(1, n_estimation_wires + 1) def qfunc(): qml.QuantumPhaseEstimation( unitary, target_wires=target_wires, estimation_wires=estimation_wires, ) decompose_once = qml.transforms.decompose(qfunc, max_expansion=1) decompose_twice = qml.transforms.decompose(qfunc, max_expansion=2)
>>> print(qml.draw(decompose_once)()) 0: โโโโโญU(M0)ยนโโโโโโโโค 1: โโHโโฐโโโโโโโโQFTโ โโค M0 = [[0.87758256+0.j 0. -0.47942554j] [0. -0.47942554j 0.87758256+0.j ]] >>> print(qml.draw(decompose_twice)()) 0: โโRZ(1.57)โโRY(0.50)โโญXโโRY(-0.50)โโRZ(-6.28)โโญXโโRZ(4.71)โโค 1: โโHโโโโโโโโโโโโโโโโโโโฐโโโโโโโโโโโโโโโโโโโโโโโโโฐโโโHโ โโโโโโโโค
Improvements ๐
qjit/jit compatibility and improvements
Quantum just-in-time (qjit) compilation
is the compilation of hybrid quantum-classical programs during execution of a program, rather than before
execution. PennyLane provides just-in-time compilation with its @qml.qjit
decorator, powered by the
Catalyst compiler.
Several templates are now compatible with qjit:
The sample-based measurements now support samples that are JAX tracers, allowing compatiblity with qjit workflows. (#6211)
The
qml.FABLE
template now returns the correct value when jit is enabled. (#6263)qml.metric_tensor
is now jit compatible. (#6468)qml.QutritBasisStatePreparation
is now jit compatible. (#6308)All PennyLane templates are now unit tested to ensure jit compatibility. (#6309)
Various improvements to fermionic operators
qml.fermi.FermiWord
andqml.fermi.FermiSentence
are now compatible with JAX arrays. (#6324)Fermionic operators interacting, in some way, with a JAX array will no longer raise an error. For example:
>>> import jax.numpy as jnp >>> w = qml.fermi.FermiWord({(0, 0) : '+', (1, 1) : '-'}) >>> jnp.array([3]) * w FermiSentence({FermiWord({(0, 0): '+', (1, 1): '-'}): Array([3], dtype=int32)})
The
qml.fermi.FermiWord
class now has ashift_operator
method to apply anti-commutator relations. (#6196)>>> w = qml.fermi.FermiWord({(0, 0): '+', (1, 1): '-'}) >>> w FermiWord({(0, 0): '+', (1, 1): '-'}) >>> w.shift_operator(0, 1) FermiSentence({FermiWord({(0, 1): '-', (1, 0): '+'}): -1})
The
qml.fermi.FermiWord
andqml.fermi.FermiSentence
classes now anadjoint
method. (#6166)>>> w = qml.fermi.FermiWord({(0, 0): '+', (1, 1): '-'}) >>> w.adjoint() FermiWord({(0, 1): '+', (1, 0): '-'})
The
to_mat
methods forqml.fermi.FermiWord
andqml.fermi.FermiSentence
now optionally return a sparse matrix with theformat
keyword argument. (#6173)>>> w = qml.fermi.FermiWord({(0, 0) : '+', (1, 1) : '-'}) >>> w.to_mat(format="dense") array([[0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j], [0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j], [0.+0.j, 1.+0.j, 0.+0.j, 0.+0.j], [0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j]]) >>> w.to_mat(format="csr") <4x4 sparse matrix of type '<class 'numpy.complex128'>' with 1 stored elements in Compressed Sparse Row format>
When printed,
qml.fermi.FermiWord
andqml.fermi.FermiSentence
now return a unique representation of the object. (#6167)>>> w = qml.fermi.FermiWord({(0, 0) : '+', (1, 1) : '-'}) >>> print(w) aโบ(0) a(1)
qml.qchem.excitations
now optionally returns fermionic operators with a newfermionic
keyword argument (defaults toFalse
). (#6171)>>> singles, doubles = excitations(electrons, orbitals, fermionic=True) >>> print(singles) [FermiWord({(0, 0): '+', (1, 2): '-'}), FermiWord({(0, 1): '+', (1, 3): '-'})]
A new optimizer
A new optimizer called
qml.MomentumQNGOptimizer
has been added. It inherits from the basicqml.QNGOptimizer
optimizer and requires one additional hyperparameter: the momentum coefficient, \(0 \leq \rho < 1\), the default value being \(\rho=0.9\). For \(\rho=0\),qml.MomentumQNGOptimizer
reduces down toqml.QNGOptimizer
. (#6240)
Other Improvements
default.tensor
can now handle mid-circuit measurements via the deferred measurement principle. (#6408)process_density_matrix
was implemented in 5StateMeasurement
subclasses:ExpVal
,Var
,Purity
,MutualInformation
, andVnEntropy
. This facilitates future support for mixed-state devices and expanded density matrix operations. Also, a fix was made in theProbabilityMP
class to useqml.math.sqrt
instead ofnp.sqrt
. (#6330)The decomposition for
qml.Qubitization
has been improved to useqml.PrepSelPrep
. (#6182)A
ReferenceQubit
device (shortname:"reference.qubit"
) has been introduced for testing purposes and referencing for future plugin development. (#6181)qml.transforms.mitigate_with_zne
now gives a clearer error message when being applied on circuits, not devices, that include channel noise. (#6346)A new function called
get_best_diff_method
has been added toqml.workflow
. (#6399)A new method called
construct_tape
has been added toqml.workflow
for users to construct single tapes from aQNode
. (#6419)An infrastructural improvement was made to PennyLane datasets that allows us to upload datasets more easily. (#6126)
qml.Hadamard
now has a more friendly alias:qml.H
. (#6450)A Boolean keyword argument called
show_wire_labels
has been added todraw
anddraw_mpl
, which hides wire labels when set toFalse
(the default isTrue
). (#6410)A new function called
sample_probs
has been added to theqml.devices.qubit
andqml.devices.qutrit_mixed
modules. This function takes probability distributions as input and returns sampled outcomes, simplifying the sampling process by separating it from other operations in the measurement chain and improving modularity. (#6354)qml.labs
has been added to the PennyLane documentation. (#6397) (#6369)A
has_sparse_matrix
property has been added toOperator
to indicate whether a sparse matrix is defined. (#6278) (#6310)qml.matrix
now works with empty objects (e.g., empty tapes, QNodes and quantum functions that do not call operations, and single operators with empty decompositions). (#6347)dev = qml.device("default.qubit", wires=1) @qml.qnode(dev) def node(): return qml.expval(qml.Z(0))
>>> qml.matrix(node)() array([[1., 0.], [0., 1.]])
PennyLane is now compatible with NumPy 2.0. (#6061) (#6258) (#6342)
PennyLane is now compatible with Jax 0.4.28. (#6255)
The
diagonalize_measurements
transform now uses a more efficient method of diagonalization when possible, based on thepauli_rep
of the relevant observables. (#6113)The
QuantumScript.copy
method now takesoperations
,measurements
,shots
andtrainable_params
as keyword arguments. If any of these are passed when copying a tape, the specified attributes will replace the copied attributes on the new tape. (#6285) (#6363)The
Hermitian
operator now has acompute_sparse_matrix
implementation. (#6225)When an observable is repeated on a tape,
tape.diagonalizing_gates
no longer returns the diagonalizing gates for each instance of the observable. Instead, the diagonalizing gates of each observable on the tape are included just once. (#6288)The number of diagonalizing gates returned in
qml.specs
now follows thelevel
keyword argument regarding whether the diagonalizing gates are modified by device, instead of always counting unprocessed diagonalizing gates. (#6290)A more sensible error message is raised from a
RecursionError
encountered when accessing properties and methods of a nestedCompositeOp
orSProd
. (#6375)By default,
qml.sum
andqml.prod
setlazy=True
, which keeps its operands nested. Given the recursive nature of such structures, if there are too many levels of nesting, aRecursionError
would occur when accessing many of the properties and methods.The performance of the decomposition of
qml.QFT
has been improved. (#6434)
Capturing and representing hybrid programs
qml.wires.Wires
now accepts JAX arrays as input. In many workflows with JAX, PennyLane may attempt to assign a JAX array to aWires
object, which will cause an error since JAX arrays are not hashable. Now, JAX arrays are validWires
types. Furthermore, aFutureWarning
is no longer raised inJAX 0.4.30+
when providing JAX tracers as input toqml.wires.Wires
. (#6312)A new function called
qml.capture.make_plxpr
has been added to take a function and create aCallable
that, when called, will return a PLxPR representation of the input function. (#6326)`Differentiation of hybrid programs via
qml.grad
andqml.jacobian
can now be captured with PLxPR. When evaluating a capturedqml.grad
(qml.jacobian
) instruction, it will dispatch tojax.grad
(jax.jacobian
), which differs from the Autograd implementation without capture. Pytree inputs and outputs are supported. (#6120) (#6127) (#6134)Unit testing for capturing nested control flow has been improved. (#6111)
Some custom primitives for the capture project can now be imported via
from pennylane.capture.primitives import *
. (#6129)All higher order primitives now use
jax.core.Jaxpr
as metadata instead of sometimes usingjax.core.ClosedJaxpr
orjax.core.Jaxpr
. (#6319)
Breaking changes ๐
Red-herring validation in
QNode.construct
has been removed, which fixed a bug withqml.GlobalPhase
. (#6373)Removing the
AllWires
validation inQNode.construct
was addressed as a solution to the following example not being able to run:@qml.qnode(qml.device('default.qubit', wires=2)) def circuit(x): qml.GlobalPhase(x, wires=0) return qml.state()
>>> circuit(0.5) array([0.87758256-0.47942554j, 0. +0.j , 1. +0.j , 0. +0.j ])
The
simplify
argument inqml.Hamiltonian
andqml.ops.LinearCombination
has been removed. Instead,qml.simplify()
can be called on the constructed operator. (#6279)The functions
qml.qinfo.classical_fisher
andqml.qinfo.quantum_fisher
have been removed and migrated to theqml.gradients
module.qml.gradients.classical_fisher
andqml.gradients.quantum_fisher
should be used instead. (#5911)Python 3.9 is no longer supported. Please update to 3.10 or newer. (#6223)
default.qubit.legacy
,default.qubit.tf
,default.qubit.torch
,default.qubit.jax
, anddefault.qubit.autograd
have been removed. Please usedefault.qubit
for all interfaces. (#6207) (#6208) (#6209) (#6210) (#6266)expand_fn
,max_expansion
,override_shots
, anddevice_batch_transform
have been removed from the signature ofqml.execute
. (#6203)max_expansion
andexpansion_strategy
have been removed from the QNode. (#6203)expansion_strategy
has been removed fromqml.draw
,qml.draw_mpl
, andqml.specs
.max_expansion
has been removed fromqml.specs
, as it had no impact on the output. (#6203)qml.transforms.hamiltonian_expand
andqml.transforms.sum_expand
have been removed. Please useqml.transforms.split_non_commuting
instead. (#6204)The
decomp_depth
keyword argument toqml.device
has been removed. (#6234)Operator.expand
has been removed. Please useqml.tape.QuantumScript(op.decomposition())
instead. (#6227)The native folding method
qml.transforms.fold_global
for theqml.transforms.mitigate_with_zne
transform no longer expands the circuit automatically. Instead, the user should applyqml.transforms.decompose
to decompose a circuit into a target gate set before applyingfold_global
ormitigate_with_zne
. (#6382)The
LightningVJPs
class has been removed, as all lightning devices now follow the new device interface. (#6420)
Deprecations ๐
The
expand_depth
andmax_expansion
arguments forqml.transforms.compile
andqml.transforms.decompositions.clifford_t_decomposition
respectively have been deprecated. (#6404)Legacy operator arithmetic has been deprecated. This includes
qml.ops.Hamiltonian
,qml.operation.Tensor
,qml.operation.enable_new_opmath
,qml.operation.disable_new_opmath
, andqml.operation.convert_to_legacy_H
. Note that when new operator arithmetic is enabled,qml.Hamiltonian
will continue to dispatch toqml.ops.LinearCombination
; this behaviour is not deprecated. For more information, check out the updated operator troubleshooting page. (#6287) (#6365)qml.pauli.PauliSentence.hamiltonian
andqml.pauli.PauliWord.hamiltonian
have been deprecated. Instead, please useqml.pauli.PauliSentence.operation
andqml.pauli.PauliWord.operation
, respectively. (#6287)qml.pauli.simplify()
has been deprecated. Instead, please useqml.simplify(op)
orop.simplify()
. (#6287)The
qml.BasisStatePreparation
template has been deprecated. Instead, useqml.BasisState
. (#6021)The
'ancilla'
argument forqml.iterative_qpe
has been deprecated. Instead, use the'aux_wire'
argument. (#6277)qml.shadows.shadow_expval
has been deprecated. Instead, use theqml.shadow_expval
measurement process. (#6277)qml.broadcast
has been deprecated. Please use Pythonfor
loops instead. (#6277)The
qml.QubitStateVector
template has been deprecated. Instead, useqml.StatePrep
. (#6172)The
qml.qinfo
module has been deprecated. Please see the respective functions in theqml.math
andqml.measurements
modules instead. (#5911)Device
,QubitDevice
, andQutritDevice
will no longer be accessible via top-level import in v0.40. They will still be accessible asqml.devices.LegacyDevice
,qml.devices.QubitDevice
, andqml.devices.QutritDevice
respectively. (#6238)QNode.gradient_fn
has been deprecated. Please useQNode.diff_method
andQNode.get_gradient_fn
instead. (#6244)
Documentation ๐
Updated
qml.spin
documentation. (#6387)Updated links to PennyLane.ai in the documentation to use the latest URL format, which excludes the
.html
prefix. (#6412)Update
qml.Qubitization
documentation based on new decomposition. (#6276)Fixed examples in the documentation of a few optimizers. (#6303) (#6315)
Corrected examples in the documentation of
qml.jacobian
. (#6283) (#6315)Fixed spelling in a number of places across the documentation. (#6280)
Add
work_wires
parameter toqml.MultiControlledX
docstring signature. (#6271)Removed ambiguity in error raised by the
PauliRot
class. (#6298)Renamed an incorrectly named test in
test_pow_ops.py
. (#6388)Removed outdated Docker description from installation page. (#6487)
Bug fixes ๐
The wire order for
Snapshot
โs now matches the wire order of the device, rather than the simulation. (#6461)Fixed a bug where
QNSPSAOptimizer
,QNGOptimizer
andMomentumQNGOptimizer
calculate invalid parameter updates if the metric tensor becomes singular. (#6471)The
default.qubit
device now supports parameter broadcasting withqml.classical_shadow
andqml.shadow_expval
. (#6301)Fixed unnecessary call of
eigvals
inqml.ops.op_math.decompositions.two_qubit_unitary.py
that was causing an error in VJP. Raises warnings to users if this essentially nondifferentiable module is used. (#6437)Patches the
math
module to function with autoray 0.7.0. (#6429)Fixed incorrect differentiation of
PrepSelPrep
when usingdiff_method="parameter-shift"
. (#6423)The
validate_device_wires
transform now raises an error if abstract wires are provided. (#6405)Fixed
qml.math.expand_matrix
for qutrit and arbitrary qudit operators. (#6398)MeasurementValue
now raises an error when it is used as a boolean. (#6386)default.qutrit
now returns integer samples. (#6385)adjoint_metric_tensor
now works with circuits containing state preparation operations. (#6358)quantum_fisher
now respects the classical Jacobian of QNodes. (#6350)qml.map_wires
can now be applied to a batch of tapes. (#6295)Fixed float-to-complex casting in various places across PennyLane. (#6260) (#6268)
Fixed a bug where zero-valued JVPs were calculated wrongly in the presence of shot vectors. (#6219)
Fixed
qml.PrepSelPrep
template to work withtorch
. (#6191)Fixed a bug where
qml.equal
now correctly comparesqml.PrepSelPrep
operators. (#6182)The
qml.QSVT
template now orders theprojector
wires first and theUA
wires second, which is the expected order of the decomposition. (#6212)The
qml.Qubitization
template now orders thecontrol
wires first and thehamiltonian
wires second, which is the expected according to other templates. (#6229)Fixed a bug where a circuit using the
autograd
interface sometimes returns nested values that are not of theautograd
interface. (#6225)Fixed a bug where a simple circuit with no parameters or only builtin/NumPy arrays as parameters returns autograd tensors. (#6225)
qml.pauli.PauliVSpace
now uses a more stable SVD-based linear independence check to avoid running intoLinAlgError: Singular matrix
. This stabilizes the usage ofqml.lie_closure
. It also introduces normalization of the basis vectorโs internal representation_M
to avoid exploding coefficients. (#6232)Fixed a bug where
csc_dot_product
is used during measurement forSum
/Hamiltonian
that contains observables that does not define a sparse matrix. (#6278) (#6310)Fixed a bug where
None
was added to the wires inqml.PhaseAdder
,qml.Adder
andqml.OutAdder
. (#6360)Fixed a test after updating to the nightly version of Catalyst. (#6362)
Fixed a bug where
CommutingEvolution
with a trainableHamiltonian
cannot be differentiated using parameter shift. (#6372)Fixed a bug where
mitigate_with_zne
loses theshots
information of the original tape. (#6444)Fixed a bug where
default.tensor
raises an error when applyingIdentity
/GlobalPhase
on no wires, andPauliRot
/MultiRZ
on a single wire. (#6448)Fixes a bug where applying
qml.ctrl
andqml.adjoint
on an operator type instead of an operator instance results in extra operators in the queue. (#6284)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Guillermo Alonso, Utkarsh Azad, Oleksandr Borysenko, Astral Cai, Yushao Chen, Isaac De Vlugt, Diksha Dhawan, Lillian M. A. Frederiksen, Pietropaolo Frisoni, Emiliano Godinez, Anthony Hayes, Austin Huang, Soran Jahangiri, Jacob Kitchen, Korbinian Kottmann, Christina Lee, William Maxwell, Erick Ochoa Lopez, Lee J. OโRiordan, Mudit Pandey, Andrija Paurevic, Alex Preciado, Ashish Kanwar Singh, David Wierichs,
- orphan
Release 0.38.0ยถ
New features since last release
Registers of wires ๐งธ
A new function called
qml.registers
has been added that lets you seamlessly create registers of wires. (#5957) (#6102)Using registers, it is easier to build large algorithms and circuits by applying gates and operations to predefined collections of wires. With
qml.registers
, you can create registers of wires by providing a dictionary whose keys are register names and whose values are the number of wires in each register.>>> wire_reg = qml.registers({"alice": 4, "bob": 3}) >>> wire_reg {'alice': Wires([0, 1, 2, 3]), 'bob': Wires([4, 5, 6])}
The resulting data structure of
qml.registers
is a dictionary with the same register names as keys, but the values areqml.wires.Wires
instances.Nesting registers within other registers can be done by providing a nested dictionary, where the ordering of wire labels is based on the order of appearance and nestedness.
>>> wire_reg = qml.registers({"alice": {"alice1": 1, "alice2": 2}, "bob": {"bob1": 2, "bob2": 1}}) >>> wire_reg {'alice1': Wires([0]), 'alice2': Wires([1, 2]), 'alice': Wires([0, 1, 2]), 'bob1': Wires([3, 4]), 'bob2': Wires([5]), 'bob': Wires([3, 4, 5])}
Since the values of the dictionary are
Wires
instances, their use within quantum circuits is very similar to that of alist
of integers.dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(): for w in wire_reg["alice"]: qml.Hadamard(w) for w in wire_reg["bob1"]: qml.RX(0.1967, wires=w) qml.CNOT(wires=[wire_reg["alice1"][0], wire_reg["bob2"][0]]) return [qml.expval(qml.Y(w)) for w in wire_reg["bob1"]] print(qml.draw(circuit)())
0: โโHโโโโโโโโโญโโโค 1: โโHโโโโโโโโโโโโค 2: โโHโโโโโโโโโโโโค 3: โโRX(0.20)โโโโโค <Y> 4: โโRX(0.20)โโโโโค <Y> 5: โโโโโโโโโโโโฐXโโค
In tandem with
qml.registers
, weโve also made the following improvements toqml.wires.Wires
:Wires
instances now have a more copy-paste friendly representation when printed. (#5958)>>> from pennylane.wires import Wires >>> w = Wires([1, 2, 3]) >>> w Wires([1, 2, 3])
Python set-based combinations are now supported by
Wires
. (#5983)This new feature unlocks the ability to combine
Wires
instances in the following ways:intersection with
&
orintersection()
:>>> wires1 = Wires([1, 2, 3]) >>> wires2 = Wires([2, 3, 4]) >>> wires1.intersection(wires2) # or wires1 & wires2 Wires([2, 3])
symmetric difference with
^
orsymmetric_difference()
:>>> wires1.symmetric_difference(wires2) # or wires1 ^ wires2 Wires([1, 4])
union with
|
orunion()
:>>> wires1.union(wires2) # or wires1 | wires2 Wires([1, 2, 3, 4])
difference with
-
ordifference()
:>>> wires1.difference(wires2) # or wires1 - wires2 Wires([1])
Quantum arithmetic operations ๐งฎ
Several new operator templates have been added to PennyLane that let you perform quantum arithmetic operations. (#6109) (#6112) (#6121)
qml.Adder
performs in-place modular addition: \(\text{Adder}(k, m)\vert x \rangle = \vert x + k \; \text{mod} \; m\rangle\).qml.PhaseAdder
is similar toqml.Adder
, but it performs in-place modular addition in the Fourier basis.qml.Multiplier
performs in-place multiplication: \(\text{Multiplier}(k, m)\vert x \rangle = \vert x \times k \; \text{mod} \; m \rangle\).qml.OutAdder
performs out-place modular addition: \(\text{OutAdder}(m)\vert x \rangle \vert y \rangle \vert b \rangle = \vert x \rangle \vert y \rangle \vert b + x + y \; \text{mod} \; m \rangle\).qml.OutMultiplier
performs out-place modular multiplication: \(\text{OutMultiplier}(m)\vert x \rangle \vert y \rangle \vert b \rangle = \vert x \rangle \vert y \rangle \vert b + x \times y \; \text{mod} \; m \rangle\).qml.ModExp
performs modular exponentiation: \(\text{ModExp}(base, m) \vert x \rangle \vert k \rangle = \vert x \rangle \vert k \times base^x \; \text{mod} \; m \rangle\).
Here is a comprehensive example that performs the following calculation:
(2 + 1) * 3 mod 7 = 2
(or010
in binary).dev = qml.device("default.qubit", shots=1) wire_reg = qml.registers({ "x_wires": 2, # |x>: stores the result of 2 + 1 = 3 "y_wires": 2, # |y>: multiples x by 3 "output_wires": 3, # stores the result of (2 + 1) * 3 m 7 = 2 "work_wires": 2 # for qml.OutMultiplier }) @qml.qnode(dev) def circuit(): # In-place addition qml.BasisEmbedding(2, wires=wire_reg["x_wires"]) qml.Adder(1, x_wires=wire_reg["x_wires"]) # add 1 to wires [0, 1] # Out-place multiplication qml.BasisEmbedding(3, wires=wire_reg["y_wires"]) qml.OutMultiplier( wire_reg["x_wires"], wire_reg["y_wires"], wire_reg["output_wires"], work_wires=wire_reg["work_wires"], mod=7 ) return qml.sample(wires=wire_reg["output_wires"])
>>> circuit() array([0, 1, 0])
Converting noise models from Qiskit โป๏ธ
Convert Qiskit noise models into a PennyLane
NoiseModel
withqml.from_qiskit_noise
. (#5996)In the last few releases, weโve added substantial improvements and new features to the Pennylane-Qiskit plugin. With this release, a new
qml.from_qiskit_noise
function allows you to convert a Qiskit noise model into a PennyLaneNoiseModel
. Here is a simple example with two quantum errors that add two different depolarizing errors based on the presence of different gates in the circuit:import pennylane as qml import qiskit_aer.noise as noise error_1 = noise.depolarizing_error(0.001, 1) # 1-qubit noise error_2 = noise.depolarizing_error(0.01, 2) # 2-qubit noise noise_model = noise.NoiseModel() noise_model.add_all_qubit_quantum_error(error_1, ['rz', 'ry']) noise_model.add_all_qubit_quantum_error(error_2, ['cx'])
>>> qml.from_qiskit_noise(noise_model) NoiseModel({ OpIn(['RZ', 'RY']): QubitChannel(num_kraus=4, num_wires=1) OpIn(['CNOT']): QubitChannel(num_kraus=16, num_wires=2) })
Under the hood, PennyLane converts each quantum error in the Qiskit noise model into an equivalent
qml.QubitChannel
operator with the same canonical Kraus representation. Currently, noise models in PennyLane do not support readout errors. As such, those will be skipped during conversion if they are present in the Qiskit noise model.Make sure to
pip install pennylane-qiskit
to access this new feature!
Substantial upgrades to mid-circuit measurements using tree-traversal ๐ณ
The
"tree-traversal"
algorithm for mid-circuit measurements (MCMs) ondefault.qubit
has been internally redesigned for better performance. (#5868)In the last release (v0.37), we introduced the tree-traversal MCM method, which was implemented in a recursive way for simplicity. However, this had the unintended consequence of very deep stack calls for circuits with many MCMs, resulting in stack overflows in some cases. With this release, weโve refactored the implementation of the tree-traversal method into an iterative approach, which solves those inefficiencies when many MCMs are present in a circuit.
The
tree-traversal
algorithm is now compatible with analytic-mode execution (shots=None
). (#5868)dev = qml.device("default.qubit") n_qubits = 5 @qml.qnode(dev, mcm_method="tree-traversal") def circuit(): for w in range(n_qubits): qml.Hadamard(w) for w in range(n_qubits - 1): qml.CNOT(wires=[w, w+1]) for w in range(n_qubits): m = qml.measure(w) qml.cond(m == 1, qml.RX)(0.1967 * (w + 1), w) return [qml.expval(qml.Z(w)) for w in range(n_qubits)]
>>> circuit() [tensor(0.00964158, requires_grad=True), tensor(0.03819446, requires_grad=True), tensor(0.08455748, requires_grad=True), tensor(0.14694258, requires_grad=True), tensor(0.2229438, requires_grad=True)]
Improvements ๐
Creating spin Hamiltonians
Three new functions are now available for creating commonly-used spin Hamiltonians in PennyLane: (#6106) (#6128)
qml.spin.transverse_ising
creates the transverse-field Ising model Hamiltonian.qml.spin.heisenberg
creates the Heisenberg model Hamiltonian.qml.spin.fermi_hubbard
creates the Fermi-Hubbard model Hamiltonian.
Each Hamiltonian can be instantiated by specifying a
lattice
, the number of unit cells,n_cells
, and the Hamiltonian parameters as keyword arguments. Here is an example with the transverse-field Ising model:>>> tfim_ham = qml.spin.transverse_ising(lattice="square", n_cells=[2, 2], coupling=0.5, h=0.2) >>> tfim_ham ( -0.5 * (Z(0) @ Z(1)) + -0.5 * (Z(0) @ Z(2)) + -0.5 * (Z(1) @ Z(3)) + -0.5 * (Z(2) @ Z(3)) + -0.2 * X(0) + -0.2 * X(1) + -0.2 * X(2) + -0.2 * X(3) )
The resulting object is a
qml.Hamiltonian
instance, making it easy to use in circuits like the following.dev = qml.device("default.qubit", shots=1) @qml.qnode(dev) def circuit(): return qml.expval(tfim_ham)
>>> circuit() -2.0
More features will be added to the
qml.spin
module in the coming releases, so stay tuned!
A Prep-Select-Prep template
A new template called
qml.PrepSelPrep
has been added that implements a block-encoding of a linear combination of unitaries. (#5756) (#5987)This operator acts as a nice wrapper for having to perform
qml.StatePrep
,qml.Select
, andqml.adjoint(qml.StatePrep)
in succession, which is quite common in many quantum algorithms (e.g., LCU and block encoding). Here is an example showing the equivalence between usingqml.PrepSelPrep
andqml.StatePrep
,qml.Select
, andqml.adjoint(qml.StatePrep)
.coeffs = [0.3, 0.1] alphas = (np.sqrt(coeffs) / np.linalg.norm(np.sqrt(coeffs))) unitaries = [qml.X(2), qml.Z(2)] lcu = qml.dot(coeffs, unitaries) control = [0, 1] def prep_sel_prep(alphas, unitaries): qml.StatePrep(alphas, wires=control, pad_with=0) qml.Select(unitaries, control=control) qml.adjoint(qml.StatePrep)(alphas, wires=control, pad_with=0) @qml.qnode(qml.device("default.qubit")) def circuit(lcu, control, alphas, unitaries): qml.PrepSelPrep(lcu, control) qml.adjoint(prep_sel_prep)(alphas, unitaries) return qml.state()
>>> import numpy as np >>> np.round(circuit(lcu, control, alphas, unitaries), decimals=2) tensor([1.+0.j -0.+0.j -0.+0.j -0.+0.j 0.+0.j 0.+0.j 0.+0.j 0.+0.j], requires_grad=True)
QChem improvements
Molecules and Hamiltonians can now be constructed for all the elements present in the periodic table. (#5821)
This new feature is made possible by integrating with the basis-set-exchange package. If loading basis sets from
basis-set-exchange
is needed for your molecule, make sure that youpip install basis-set-exchange
and setload_data=True
.symbols = ['Ti', 'Ti'] geometry = np.array([[0.0, 0.0, -1.1967], [0.0, 0.0, 1.1967]], requires_grad=True) mol = qml.qchem.Molecule(symbols, geometry, load_data=True)
>>> mol.n_electrons 44
qml.UCCSD
now accepts an additional optional argument,n_repeats
, which defines the number of times the UCCSD template is repeated. This can improve the accuracy of the template by reducing the Trotter error, but would result in deeper circuits. (#5801)The
qml.qchem.qubit_observable
function has been modified to return an ascending wire order for molecular Hamiltonians. (#5950)A new method called
to_mat
has been added to theqml.FermiWord
andqml.FermiSentence
classes, which allows for computing the matrix representation of these Fermi operators. (#5920)
Improvements to operators
qml.GlobalPhase
now supports parameter broadcasting. (#5923)qml.Hermitian
now has acompute_decomposition
method. (#6062)The implementation of
qml.PhaseShift
,qml.S
, andqml.T
has been improved, resulting in faster circuit execution times. (#5876)The
qml.CNOT
operator no longer decomposes into itself. Instead, it raises aqml.DecompositionUndefinedError
. (#6039)
Mid-circuit measurements
The
qml.dynamic_one_shot
transform now supports circuits using the"tensorflow"
interface. (#5973)If the conditional does not include a mid-circuit measurement, then
qml.cond
will automatically evaluate conditionals using standard Python control flow. (#6016)This allows
qml.cond
to be used to represent a wider range of conditionals:dev = qml.device("default.qubit", wires=1) @qml.qnode(dev) def circuit(x): c = qml.cond(x > 2.7, qml.RX, qml.RZ) c(x, wires=0) return qml.probs(wires=0)
>>> print(qml.draw(circuit)(3.8)) 0: โโRX(3.80)โโค Probs >>> print(qml.draw(circuit)(0.54)) 0: โโRZ(0.54)โโค Probs
Transforms
qml.transforms.single_qubit_fusion
andqml.transforms.merge_rotations
now respect global phases. (#6031)A new transform called
qml.transforms.diagonalize_measurements
has been added. This transform converts measurements to the computational basis by applying the relevant diagonalizing gates. It can be set to diagonalize only a subset of the base observables{qml.X, qml.Y, qml.Z, qml.Hadamard}
. (#5829)A new transform called
split_to_single_terms
has been added. This transform splits expectation values of sums into multiple single-term measurements on a single tape, providing better support for simulators that can handle non-commuting observables but donโt natively support multi-term observables. (#5884)New functionality has been added to natively support exponential extrapolation when using
qml.transforms.mitigate_with_zne
. This allows users to have more control over the error mitigation protocol without needing to add further dependencies. (#5972)
Capturing and representing hybrid programs
qml.for_loop
now supportsrange
-like syntax with defaultstep=1
. (#6068)Applying
adjoint
andctrl
to a quantum function can now be captured into plxpr. Furthermore, theqml.cond
function can be captured into plxpr. (#5966) (#5967) (#5999) (#6058)During experimental program capture, functions that accept and/or return
pytree
structures can now be handled in theqml.QNode
call,qml.cond
,qml.for_loop
andqml.while_loop
. (#6081)During experimental program capture, QNodes can now use closure variables. (#6052)
Mid-circuit measurements can now be captured with
qml.capture
enabled. (#6015)qml.for_loop
can now be captured into plxpr. (#6041) (#6064)qml.for_loop
andqml.while_loop
now fall back to standard Python control flow if@qjit
is not present, allowing the same code to work with and without@qjit
without any rewrites. (#6014)dev = qml.device("lightning.qubit", wires=3) @qml.qnode(dev) def circuit(x, n): @qml.for_loop(0, n, 1) def init_state(i): qml.Hadamard(wires=i) init_state() @qml.for_loop(0, n, 1) def apply_operations(i, x): qml.RX(x, wires=i) @qml.for_loop(i + 1, n, 1) def inner(j): qml.CRY(x**2, [i, j]) inner() return jnp.sin(x) apply_operations(x) return qml.probs()
>>> print(qml.draw(circuit)(0.5, 3)) 0: โโHโโRX(0.50)โโญโโโโโโโโโโญโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค Probs 1: โโHโโโโโโโโโโโโฐRY(0.25)โโโโโโโโโโโโRX(0.48)โโญโโโโโโโโโโโโโโโโโโโโค Probs 2: โโHโโโโโโโโโโโโโโโโโโโโโโฐRY(0.25)โโโโโโโโโโโโฐRY(0.23)โโRX(0.46)โโค Probs >>> circuit(0.5, 3) array([0.125 , 0.125 , 0.09949758, 0.15050242, 0.07594666, 0.11917543, 0.08942104, 0.21545687]) >>> qml.qjit(circuit)(0.5, 3) Array([0.125 , 0.125 , 0.09949758, 0.15050242, 0.07594666, 0.11917543, 0.08942104, 0.21545687], dtype=float64)
Community contributions ๐ฅณ
Fixed a bug in
qml.ThermalRelaxationError
where there was a typo fromtq
totg
. (#5988)Readout error has been added using parameters
readout_relaxation_probs
andreadout_misclassification_probs
on thedefault.qutrit.mixed
device. These parameters add aqml.QutritAmplitudeDamping
and aqml.TritFlip
channel, respectively, after measurement diagonalization. The amplitude damping error represents the potential for relaxation to occur during longer measurements. The trit flip error represents misclassification during readout. (#5842)qml.ops.qubit.BasisStateProjector
now has acompute_sparse_matrix
method that computes the sparse CSR matrix representation of the projector onto the given basis state. (#5790)
Other improvements
qml.pauli.group_observables
now usesrustworkx
colouring algorithms to solve the Minimum Clique Cover problem, resulting in orders of magnitude performance improvements. (#6043)This adds two new options for the
method
argument:dsatur
(degree of saturation) andgis
(independent set). In addition, the creation of the adjacency matrix now takes advantage of the symplectic representation of the Pauli observables.Additionally, a new function called
qml.pauli.compute_partition_indices
has been added to calculate the indices from the partitioned observables more efficiently. These changes improve the wall time ofqml.LinearCombination.compute_grouping
and thegrouping_type='qwc'
by orders of magnitude.qml.counts
measurements withall_outcomes=True
can now be used with JAX jitting. Additionally, measurements broadcasted across all available wires (e.g.,qml.probs()
) can now be used with JAX jit and devices that allow dynamic numbers of wires (only'default.qubit'
currently). (#6108)qml.ops.op_math.ctrl_decomp_zyz
can now decompose special unitaries with multiple control wires. (#6042)A new method called
process_density_matrix
has been added to theProbabilityMP
andDensityMatrixMP
measurement processes, allowing for more efficient handling of quantum density matrices, particularly with batch processing support. This method simplifies the calculation of probabilities from quantum states represented as density matrices. (#5830)SProd.terms
now flattens out the terms if the base is a multi-term observable. (#5885)qml.QNGOptimizer
now supports cost functions with multiple arguments, updating each argument independently. (#5926)semantic_version
has been removed from the list of required packages in PennyLane. (#5836)qml.devices.LegacyDeviceFacade
has been added to map the legacy devices to the new device interface, making it easier for developers to develop legacy devices. (#5927)StateMP.process_state
now defines rules incast_to_complex
for complex casting, avoiding a superfluous statevector copy in PennyLane-Lightning simulations. (#5995)QuantumScript.hash
is now cached, leading to performance improvements. (#5919)Observable validation for
default.qubit
is now based on execution mode (analytic vs. finite shots) and measurement type (sample measurement vs. state measurement). This improves our error handling when, for example, non-hermitian operators are given toqml.expval
. (#5890)A new
is_leaf
parameter has been added to the functionflatten
in theqml.pytrees
module. This is to allow for node flattening to be stopped for any node where theis_leaf
optional argument evaluates to beingTrue
. (#6107)A progress bar has been added to
qml.data.load()
when downloading a dataset. (#5560)Upgraded and simplified
StatePrep
andAmplitudeEmbedding
templates. (#6034) (#6170)Upgraded and simplified
BasisState
andBasisEmbedding
templates. (#6021)
Breaking changes ๐
MeasurementProcess.shape(shots: Shots, device:Device)
is nowMeasurementProcess.shape(shots: Optional[int], num_device_wires:int = 0)
. This has been done to allow for jitting when a measurement is broadcasted across all available wires, but the device does not specify wires. (#6108)If the shape of a probability measurement is affected by a
Device.cutoff
property, it will no longer work with jitting. (#6108)qml.GlobalPhase
is considered non-differentiable with tape transforms. As a consequence,qml.gradients.finite_diff
andqml.gradients.spsa_grad
no longer support differentiatingqml.GlobalPhase
with state-based outputs. (#5620)The
CircuitGraph.graph
rustworkx
graph now stores indices into the circuit as the node labels, instead of the operator/ measurement itself. This allows the same operator to occur multiple times in the circuit. (#5907)The
queue_idx
attribute has been removed from theOperator
,CompositeOp
, andSymbolicOp
classes. (#6005)qml.from_qasm
no longer removes measurements from the QASM code. Usemeasurements=[]
to remove measurements from the original circuit. (#5982)qml.transforms.map_batch_transform
has been removed, since transforms can be applied directly to a batch of tapes. Seeqml.transform
for more information. (#5981)QuantumScript.interface
has been removed. (#5980)
Deprecations ๐
The
decomp_depth
argument inqml.device
has been deprecated. (#6026)The
max_expansion
argument inqml.QNode
has been deprecated. (#6026)The
expansion_strategy
attributeqml.QNode
has been deprecated. (#5989)The
expansion_strategy
argument has been deprecated in all ofqml.draw
,qml.draw_mpl
, andqml.specs
. Thelevel
argument should be used instead. (#5989)Operator.expand
has been deprecated. Users should simply useqml.tape.QuantumScript(op.decomposition())
for equivalent behaviour. (#5994)qml.transforms.sum_expand
andqml.transforms.hamiltonian_expand
have been deprecated. Users should instead useqml.transforms.split_non_commuting
for equivalent behaviour. (#6003)The
expand_fn
argument inqml.execute
has been deprecated. Instead, please create aqml.transforms.core.TransformProgram
with the desired preprocessing and pass it to thetransform_program
argument ofqml.execute
. (#5984)The
max_expansion
argument inqml.execute
has been deprecated. Instead, please useqml.devices.preprocess.decompose
with the desired expansion level, add it to aqml.transforms.core.TransformProgram
and pass it to thetransform_program
argument ofqml.execute
. (#5984)The
override_shots
argument inqml.execute
has been deprecated. Instead, please add the shots to theQuantumTape
s to be executed. (#5984)The
device_batch_transform
argument inqml.execute
has been deprecated. Instead, please create aqml.transforms.core.TransformProgram
with the desired preprocessing and pass it to thetransform_program
argument ofqml.execute
. (#5984)qml.qinfo.classical_fisher
andqml.qinfo.quantum_fisher
have been deprecated. Instead, useqml.gradients.classical_fisher
andqml.gradients.quantum_fisher
. (#5985)The legacy devices
default.qubit.{autograd,torch,tf,jax,legacy}
have been deprecated. Instead, usedefault.qubit
, as it now supports backpropagation through the several backends. (#5997)The logic for internally switching a device for a different backpropagation compatible device is now deprecated, as it was in place for the deprecated
default.qubit.legacy
. (#6032)
Documentation ๐
The docstring for
qml.qinfo.quantum_fisher
, regarding the internally used functions and potentially required auxiliary wires, has been improved. (#6074)The docstring for
QuantumScript.expand
andqml.tape.tape.expand_tape
has been improved. (#5974)
Bug fixes ๐
The sparse matrix can now be computed for a product operator when one operand is a
GlobalPhase
on no wires. (#6197)For
default.qubit
, JAX is now used for sampling whenever the state is a JAX array. This fixes normalization issues that can occur when the state uses 32-bit precision. (#6190)Fix Pytree serialization of operators with empty shot vectors (#6155)
Fixes an error in the
dynamic_one_shot
transform when used with sampling a single shot. (#6149)qml.transforms.pattern_matching_optimization
now preserves the tape measurements. (#6153)qml.transforms.broadcast_expand
no longer squeezes out batch sizes of size 1, as a batch size of 1 is still a batch size. (#6147)Catalyst replaced
argnum
withargnums
in gradient related functions, therefore we updated the Catalyst calls to those functions in PennyLane. (#6117)fuse_rot_angles
now returns NaN instead of incorrect derivatives at singular points. (#6031)qml.GlobalPhase
andqml.Identity
can now be captured with plxpr when acting on no wires. (#6060)Fixed
jax.grad
andjax.jit
to work forqml.AmplitudeEmbedding
,qml.StatePrep
andqml.MottonenStatePreparation
. (#5620)Fixed a bug in
qml.center
that omitted elements from the center if they were linear combinations of input elements. (#6049)Fix a bug where the global phase returned by
one_qubit_decomposition
gained a broadcasting dimension. (#5923)Fixed a bug in
qml.SPSAOptimizer
that ignored keyword arguments in the objective function. (#6027)Fixed
dynamic_one_shot
for use with devices using the old device API, sinceoverride_shots
was deprecated. (#6024)CircuitGraph
can now handle circuits with the same operation instance occuring multiple times. (#5907)qml.QSVT
has been updated to store wire order correctly. (#5959)qml.devices.qubit.measure_with_samples
now returns the correct result if the provided measurements contain a sum of operators acting on the same wire. (#5978)qml.AmplitudeEmbedding
has better support for features using low precision integer data types. (#5969)qml.BasisState
andqml.BasisEmbedding
now works with jax.jit,lightning.qubit
, and give the correct decomposition. (#6021)Jacobian shape has been fixed for measurements with dimension in
qml.gradients.vjp.compute_vjp_single
. (5986)qml.lie_closure
now works with sums of Paulis. (#6023)Workflows that parameterize the coefficients of
qml.exp
are now jit-compatible. (#6082)Fixed a bug where
CompositeOp.overlapping_ops
changes the original ordering of operators, causing an incorrect matrix to be generated forProd
withSum
as operands. (#6091)qml.qsvt
now works with โWxโ convention and any number of angles. (#6105)Basis set data from the Basis Set Exchange library can now be loaded for elements with
SPD
-type orbitals. (#6159)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Tarun Kumar Allamsetty, Guillermo Alonso, Ali Asadi, Utkarsh Azad, Tonmoy T. Bhattacharya, Gabriel Bottrill, Jack Brown, Ahmed Darwish, Astral Cai, Yushao Chen, Ahmed Darwish, Diksha Dhawan Maja Franz, Lillian M. A. Frederiksen, Pietropaolo Frisoni, Emiliano Godinez, Austin Huang, Renke Huang, Josh Izaac, Soran Jahangiri, Korbinian Kottmann, Christina Lee, Jorge Martinez de Lejarza, William Maxwell, Vincent Michaud-Rioux, Anurav Modak, Mudit Pandey, Andrija Paurevic, Erik Schultheis, nate stemen, David Wierichs,
- orphan
Release 0.37.0ยถ
New features since last release
Execute wide circuits with Default Tensor ๐
A new
default.tensor
device is now available for performing tensor network and matrix product state simulations of quantum circuits using the quimb backend. (#5699) (#5744) (#5786) (#5795)Either method can be selected when instantiating the
default.tensor
device by setting themethod
keyword argument to"tn"
(tensor network) or"mps"
(matrix product state).There are several templates in PennyLane that are tensor-network focused, which are excellent candidates for the
"tn"
method fordefault.tensor
. The following example shows how a circuit comprising gates in a tree tensor network architecture can be efficiently simulated usingmethod="tn"
.import pennylane as qml n_wires = 16 dev = qml.device("default.tensor", method="tn") def block(weights, wires): qml.CNOT(wires=[wires[0], wires[1]]) qml.RY(weights[0], wires=wires[0]) qml.RY(weights[1], wires=wires[1]) n_block_wires = 2 n_params_block = 2 n_blocks = qml.TTN.get_n_blocks(range(n_wires), n_block_wires) template_weights = [[0.1, -0.3]] * n_blocks @qml.qnode(dev) def circuit(template_weights): for i in range(n_wires): qml.Hadamard(i) qml.TTN(range(n_wires), n_block_wires, block, n_params_block, template_weights) return qml.expval(qml.Z(n_wires - 1))
>>> circuit(template_weights) 0.3839174759751649
For matrix product state simulations (
method="mps"
), we can make the execution be approximate by settingmax_bond_dim
(see the deviceโs documentation for more details). The maximum bond dimension has implications for the speed of the simulation and lets us control the degree of the approximation, as shown in the following example. First, set up the circuit:import numpy as np n_layers = 10 n_wires = 10 initial_shape, weights_shape = qml.SimplifiedTwoDesign.shape(n_layers, n_wires) np.random.seed(1967) initial_layer_weights = np.random.random(initial_shape) weights = np.random.random(weights_shape) def f(): qml.SimplifiedTwoDesign(initial_layer_weights, weights, range(n_wires)) return qml.expval(qml.Z(0))
The
default.tensor
device is instantiated with amax_bond_dim
value:dev_dq = qml.device("default.qubit") value_dq = qml.QNode(f, dev_dq)() dev_mps = qml.device("default.tensor", max_bond_dim=5) value_mps = qml.QNode(f, dev_mps)()
With this bond dimension, the expectation values calculated for
default.qubit
anddefault.tensor
are different:>>> np.abs(value_dq - value_mps) tensor(0.0253213, requires_grad=True)
Learn more about
default.tensor
and how to configure it by visiting the how-to guide.
Add noise models to your quantum circuits ๐บ
Support for building noise models and applying them to a quantum circuit has been added via the
NoiseModel
class and anadd_noise
transform. (#5674) (#5684) (#5718)Under the hood, PennyLaneโs approach to noise models is insertion-based, meaning that noise is included by inserting additional operators (gates or channels) that describe the noise into the quantum circuit. Creating a
NoiseModel
boils down to defining Boolean conditions under which specific noisy operations are inserted. There are several ways to specify conditions for adding noisy operations:qml.noise.op_eq(op)
: if the operatorop
is encountered in the circuit, add noise.qml.noise.op_in(ops)
: if any operators inops
are encountered in the circuit, add noise.qml.noise.wires_eq(wires)
: if an operator is applied towires
, add noise.qml.noise.wires_in(wires)
: if an operator is applied to any wire inwires
, add noise.custom noise conditions: custom conditions can be defined as functions decorated with
qml.BooleanFn
that return a Boolean value. For example, the following function will insert noise if aqml.RY
operator is encountered with an angle of rotation that is less than0.5
:@qml.BooleanFn def c0(op): return isinstance(op, qml.RY) and op.parameters[0] < 0.5
Conditions can also be combined together with
&
,and
,|
, etc. Once the conditions under which noise is to be inserted have been stated, we can specify exactly what noise is inserted with the following:qml.noise.partial_wires(op)
: insertop
on the wires that are specified by the condition that triggers adding this noisecustom noise operations: custom noise can be specified by defining a standard quantum function like below.
def n0(op, **kwargs): qml.RY(op.parameters[0] * 0.05, wires=op.wires)
With that, we can create a
qml.NoiseModel
object whose argument must be a dictionary mapping conditions to noise:c1 = qml.noise.op_eq(qml.X) & qml.noise.wires_in([0, 1]) n1 = qml.noise.partial_wires(qml.AmplitudeDamping, 0.4) noise_model = qml.NoiseModel({c0: n0, c1: n1})
>>> noise_model NoiseModel({ BooleanFn(c0): n0 OpEq(PauliX) | WiresIn([0, 1]): AmplitudeDamping(gamma=0.4) })
The noise model created can then be added to a QNode with
qml.add_noise
:dev = qml.device("lightning.qubit", wires=3) @qml.qnode(dev) def circuit(): qml.Y(0) qml.CNOT([0, 1]) qml.RY(0.3, wires=2) # triggers c0 qml.X(1) # triggers c1 return qml.state()
>>> print(qml.draw(circuit)()) 0: โโYโโโโโโโโโญโโโโโโค State 1: โโโโโโโโโโโโฐXโโXโโค State 2: โโRY(0.30)โโโโโโโโค State >>> circuit = qml.add_noise(circuit, noise_model) >>> print(qml.draw(circuit)()) 0: โโYโโโโโโโโโญโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค State 1: โโโโโโโโโโโโฐXโโโโโโโโโXโโAmplitudeDamping(0.40)โโค State 2: โโRY(0.30)โโRY(0.01)โโโโโโโโโโโโโโโโโโโโโโโโโโโโโค State
If more than one transform is applied to a QNode, control over when/where the
add_noise
transform is applied in relation to the other transforms can be specified with thelevel
keyword argument. By default,add_noise
is applied after all the transforms that have been manually applied to the QNode until that point. To learn more about this new functionality, check out our noise module documentation and keep your eyes peeled for an in-depth demo!
Catch bugs with the PennyLane debugger ๐ซ๐
The new PennyLane quantum debugger allows pausing simulation via the
qml.breakpoint()
command and provides tools for analyzing quantum circuits during execution. (#5680) (#5749) (#5789)This includes monitoring the circuit via measurements using
qml.debug_state()
,qml.debug_probs()
,qml.debug_expval()
, andqml.debug_tape()
, stepping through the operations in a quantum circuit, and interactively adding operations during execution.Including
qml.breakpoint()
in a circuit will cause the simulation to pause during execution and bring up the interactive console. For example, consider the following code in a Python file calledscript.py
:@qml.qnode(qml.device('default.qubit', wires=(0,1,2))) def circuit(x): qml.Hadamard(wires=0) qml.CNOT(wires=(0,2)) qml.breakpoint() qml.RX(x, wires=1) qml.RY(x, wires=2) qml.breakpoint() return qml.sample() circuit(1.2345)
Upon executing
script.py
, the simulation pauses at the first breakpoint:> /Users/your/path/to/script.py(8)circuit() -> qml.RX(x, wires=1) (pldb):
While debugging, we can access circuit information. For example,
qml.debug_tape()
returns the tape of the circuit, giving access to its operations and drawing:[pldb] tape = qml.debug_tape() [pldb] print(tape.draw(wire_order=[0,1,2])) 0: โโHโโญโโโค 2: โโโโโฐXโโค [pldb] tape.operations [Hadamard(wires=[0]), CNOT(wires=[0, 2])]
While
qml.debug_state()
is equivalent toqml.state()
and gives the current state:[pldb] print(qml.debug_state()) [0.70710678+0.j 0. +0.j 0. +0.j 0. +0.j 1. +0.j 0.70710678+0.j 0. +0.j 0. +0.j]
Other debugger functions like
qml.debug_probs()
andqml.debug_expval()
also function like their simulation counterparts (qml.probs
andqml.expval
, respectively) and are described in more detail in the debugger documentationAdditionally, standard debugging commands are available to navigate through code, including
list
,longlist
,next
,continue
, andquit
, as described in the debugging documentation.Finally, to modify a circuit mid-run, simply call the desired PennyLane operations:
[pldb] qml.CNOT(wires=(0,2)) CNOT(wires=[0, 2]) [pldb] print(qml.debug_tape().draw(wire_order=[0,1,2])) 0: โโHโโญโโโญโโโค 2: โโโโโฐXโโฐXโโค
Stay tuned for an in-depth demonstration on using this feature with real-world examples!
Convert between OpenFermion and PennyLane ๐ค
Two new functions called
qml.from_openfermion
andqml.to_openfermion
are now available to convert between OpenFermion and PennyLane objects. This includes both fermionic and qubit operators. (#5773) (#5808) (#5881)For fermionic operators:
>>> import openfermion >>> of_fermionic = openfermion.FermionOperator('0^ 2') >>> type(of_fermionic) <class 'openfermion.ops.operators.fermion_operator.FermionOperator'> >>> pl_fermionic = qml.from_openfermion(of_fermionic) >>> type(pl_fermionic) <class 'pennylane.fermi.fermionic.FermiWord'> >>> print(pl_fermionic) aโบ(0) a(2)
And for qubit operators:
>>> of_qubit = 0.5 * openfermion.QubitOperator('X0 X5') >>> pl_qubit = qml.from_openfermion(of_qubit) >>> print(pl_qubit) 0.5 * (X(0) @ X(5))
Better control over when drawing and specs take place ๐๏ธ
It is now possible to control the stage at which
qml.draw
,qml.draw_mpl
, andqml.specs
occur within a QNodeโs transform program. (#5855) (#5781)Consider the following circuit which has multiple transforms applied:
@qml.transforms.split_non_commuting @qml.transforms.cancel_inverses @qml.transforms.merge_rotations @qml.qnode(qml.device("default.qubit")) def f(): qml.Hadamard(0) qml.Y(0) qml.RX(0.4, 0) qml.RX(-0.4, 0) qml.Y(0) return qml.expval(qml.X(0) + 2 * qml.Y(0))
We can specify a
level
value when usingqml.draw()
:>>> print(qml.draw(f, level=0)()) # input program 0: โโHโโYโโRX(0.40)โโRX(-0.40)โโYโโค <X+(2.00*Y)> >>> print(qml.draw(f, level=1)()) # rotations merged 0: โโHโโYโโYโโค <X+(2.00*Y)> >>> print(qml.draw(f, level=2)()) # inverses cancelled 0: โโHโโค <X+(2.00*Y)> >>> print(qml.draw(f, level=3)()) # Hamiltonian expanded 0: โโHโโค <X> 0: โโHโโค <Y>
The qml.workflow.get_transform_program function can be used to see the full transform program.
>>> qml.workflow.get_transform_program(f) TransformProgram(merge_rotations, cancel_inverses, split_non_commuting, validate_device_wires, mid_circuit_measurements, decompose, validate_measurements, validate_observables, no_sampling)
Note that additional transforms can be added automatically from device preprocessing or gradient calculations. Rather than providing an integer value to
level
, it is possible to target the"user"
,"gradient"
or"device"
stages:n_wires = 3 x = np.random.random((2, n_wires)) @qml.qnode(qml.device("default.qubit")) def f(): qml.BasicEntanglerLayers(x, range(n_wires)) return qml.expval(qml.X(0))
>>> print(qml.draw(f, level="device")()) 0: โโRX(0.28)โโญโโโโโโญXโโRX(0.70)โโญโโโโโโญXโโค <X> 1: โโRX(0.52)โโฐXโโญโโโโโโRX(0.65)โโฐXโโญโโโโโโค 2: โโRX(0.00)โโโโโฐXโโฐโโโRX(0.03)โโโโโฐXโโฐโโโค
Improvements ๐
Community contributions, including UnitaryHACK ๐
default.clifford
now supports arbitrary state-based measurements withqml.Snapshot
. (#5794)qml.equal
now properly handlesPow
,Adjoint
,Exp
, andSProd
operators as arguments across different interfaces and tolerances with the addition of four new keyword arguments:check_interface
,check_trainability
,atol
andrtol
. (#5668)The implementation for
qml.assert_equal
has been updated forOperator
,Controlled
,Adjoint
,Pow
,Exp
,SProd
,ControlledSequence
,Prod
,Sum
,Tensor
andHamiltonian
instances. (#5780) (#5877)qml.from_qasm
now supports the ability to convert mid-circuit measurements fromOpenQASM 2
code, and it can now also take an optional argument to specify a list of measurements to be performed at the end of the circuit, just likeqml.from_qiskit
. (#5818)Four new operators have been added for simulating noise on the
default.qutrit.mixed
device: (#5502) (#5793) (#5503) (#5757) (#5799) (#5784)qml.QutritDepolarizingChannel
: a channel that adds depolarizing noise.qml.QutritChannel
: enables the specification of noise using a collection of (3x3) Kraus matrices.qml.QutritAmplitudeDamping
: a channel that adds noise processes modelled by amplitude damping.qml.TritFlip
: a channel that adds trit flip errors, such as misclassification.
Faster and more flexible mid-circuit measurements
The
default.qubit
device supports a depth-first tree-traversal algorithm to accelerate native mid-circuit measurement execution. Accessible through the QNode argumentmcm_method="tree-traversal"
, this new implementation supports classical control, collecting statistics, and post-selection, along with all measurements enabled withqml.dynamic_one_shot
. More information about this new mid-circuit measurement method can be found on our measurement documentation page. (#5180)qml.QNode
and the@qml.qnode
decorator now accept two new keyword arguments:postselect_mode
andmcm_method
. These keyword arguments can be used to configure how the device should behave when running circuits with mid-circuit measurements. (#5679) (#5833) (#5850)postselect_mode="hw-like"
indicates to devices to discard invalid shots when postselecting mid-circuit measurements. Usepostselect_mode="fill-shots"
to unconditionally sample the postselected value, thus making all samples valid. This is equivalent to sampling until the number of valid samples matches the total number of shots.mcm_method
will indicate which strategy to use for running circuits with mid-circuit measurements. Usemcm_method="deferred"
to use the deferred measurements principle, ormcm_method="one-shot"
to execute once for each shot. Ifqml.qjit
is being used (the Catalyst compiler),mcm_method="single-branch-statistics"
is also available. Using this method, a single branch of the execution tree will be randomly explored.
The
dynamic_one_shot
transform received a few improvements:When using
defer_measurements
with postselection, operations that will never be active due to the postselected state are skipped in the transformed quantum circuit. In addition, postselected controls are skipped, as they are evaluated when the transform is applied. This optimization feature can be turned off by settingreduce_postselected=False
. (#5558)Consider a simple circuit with three mid-circuit measurements, two of which are postselecting, and a single gate conditioned on those measurements:
@qml.qnode(qml.device("default.qubit")) def node(x): qml.RX(x, 0) qml.RX(x, 1) qml.RX(x, 2) mcm0 = qml.measure(0, postselect=0, reset=False) mcm1 = qml.measure(1, postselect=None, reset=True) mcm2 = qml.measure(2, postselect=1, reset=False) qml.cond(mcm0 + mcm1 + mcm2 == 1, qml.RX)(0.5, 3) return qml.expval(qml.Z(0) @ qml.Z(3))
Without the new optimization, we obtain three gates, each controlled on the three measured qubits. They correspond to the combinations of controls that satisfy the condition
mcm0 + mcm1 + mcm2 == 1
:>>> print(qml.draw(qml.defer_measurements(node, reduce_postselected=False))(0.6)) 0: โโRX(0.60)โโ|0โฉโจ0|โโญโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โญ<Z@Z> 1: โโRX(0.60)โโโโโโโโโโโโโญโโโญXโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โ 2: โโRX(0.60)โโโโโโโโโโโโโโโโโโโ|1โฉโจ1|โโญโโโโโโโโโโญโโโโโโโโโโญโโโโโโโโโโค โ 3: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโRX(0.50)โโRX(0.50)โโRX(0.50)โโค โฐ<Z@Z> 4: โโโโโโโโโโโโโโโโโโโโฐXโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค 5: โโโโโโโโโโโโโโโโโโโโโโโฐXโโฐโโโโโโโโโโโฐโโโโโโโโโโฐโโโโโโโโโโฐโโโโโโโโโโค
If we do not explicitly deactivate the optimization, we obtain a much simpler circuit:
>>> print(qml.draw(qml.defer_measurements(node))(0.6)) 0: โโRX(0.60)โโ|0โฉโจ0|โโญโโโโโโโโโโโโโโโโโโโค โญ<Z@Z> 1: โโRX(0.60)โโโโโโโโโโโโโญโโโญXโโโโโโโโโโโโค โ 2: โโRX(0.60)โโโโโโโโโโโโโโโโโโโ|1โฉโจ1|โโโโค โ 3: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโญRX(0.50)โโค โฐ<Z@Z> 4: โโโโโโโโโโโโโโโโโโโโฐXโโโโโโโโโโโโโโโโโโค 5: โโโโโโโโโโโโโโโโโโโโโโโฐXโโฐโโโฐโโโโโโโโโโค
There is only one controlled gate with only one control wire.
Mid-circuit measurement tests have been streamlined and refactored, removing most end-to-end tests from the native MCM test file, but keeping one that validates multiple mid-circuit measurements with any allowed return and interface end-to-end tests. (#5787)
Access to QROM
The QROM algorithm is now available in PennyLane with
qml.QROM
. This template allows you to enter classical data in the form of bitstrings. (#5688)bitstrings = ["010", "111", "110", "000"] dev = qml.device("default.qubit", shots = 1) @qml.qnode(dev) def circuit(): qml.BasisEmbedding(2, wires = [0,1]) qml.QROM(bitstrings = bitstrings, control_wires = [0,1], target_wires = [2,3,4], work_wires = [5,6,7]) return qml.sample(wires = [2,3,4])
>>> print(circuit()) [1 1 0]
Capturing and representing hybrid programs
A number of templates have been updated to be valid PyTrees and PennyLane operations. (#5698)
PennyLane operators, measurements, and QNodes can now automatically be captured as instructions in JAXPR. (#5564) (#5511) (#5708) (#5523) (#5686) (#5889)
The
qml.PyTrees
module now hasflatten
andunflatten
methods for serializing PyTrees. (#5701)qml.sample
can now be used on Boolean values representing mid-circuit measurement results in traced quantum functions. This feature is used with Catalyst to enable the patternm = measure(0); qml.sample(m)
. (#5673)
Quantum chemistry
The
qml.qchem.Molecule
object received a few improvements:The
qml.qchem.molecular_hamiltonian
function now supports parity and Bravyi-Kitaev mappings. (#5657)qml.qchem.molecular_dipole
function has been added for calculating the dipole operator using the"dhf"
and"openfermion"
backends. (#5764)The qchem module now has dedicated functions for calling the
pyscf
andopenfermion
backends and themolecular_hamiltonian
andmolecular_dipole
functions have been moved tohamiltonian
anddipole
modules. (#5553) (#5863)More fermionic-to-qubit tests have been added to cover cases when the mapped operator is different for various mapping schemes. (#5873)
Easier development
Logging now allows for an easier opt-in across the stack and support has been extended to Catalyst. (#5528)
Three new Pytest markers have been added for easier management of our test suite:
unit
,integration
andsystem
. (#5517)
Other improvements
qml.MultiControlledX
can now be decomposed even when nowork_wires
are provided. The implementation returns \(\mathcal{O}(\mbox{len(control wires)}^2)\) operations and is applicable for any multi-controlled unitary gate. This decomposition is provided in arXiv:quant-ph/9503016. (#5735)A new function called
expectation_value
has been added toqml.math
to calculate the expectation value of a matrix for pure states. (#4484)>>> state_vector = [1/np.sqrt(2), 0, 1/np.sqrt(2), 0] >>> operator_matrix = qml.matrix(qml.PauliZ(0), wire_order=[0,1]) >>> qml.math.expectation_value(operator_matrix, state_vector) tensor(-2.23711432e-17+0.j, requires_grad=True)
param_shift
with thebroadcast=True
option now supports shot vectors and multiple measurements. (#5667)qml.TrotterProduct
is now compatible with resource tracking by inheriting fromResourcesOperation
. (#5680)packaging
is now a required package in PennyLane. (#5769)qml.ctrl
now works with tuple-valuedcontrol_values
when applied to any already controlled operation. (#5725)The sorting order of parameter-shift terms is now guaranteed to resolve ties in the absolute value with the sign of the shifts. (#5582)
qml.transforms.split_non_commuting
can now handle circuits containing measurements of multi-term observables. (#5729) (#5838) (#5828) (#5869) (#5939) (#5945)qml.devices.LegacyDevice
is now an alias forqml.Device
, so it is easier to distinguish it fromqml.devices.Device
, which follows the new device API. (#5581)The
dtype
foreigvals
ofX
,Y
,Z
andHadamard
is changed fromint
tofloat
, making them consistent with the other observables. Thedtype
of the returned values when sampling these observables (e.g.qml.sample(X(0))
) is also changed tofloat
. (#5607)The framework for the development of an
assert_equal
function for testing operator comparison has been set up. (#5634) (#5858)The
decompose
transform has anerror
keyword argument to specify the type of error that should be raised, allowing error types to be more consistent with the context thedecompose
function is used in. (#5669)Empty initialization of
PauliVSpace
is permitted. (#5675)qml.tape.QuantumScript
properties are only calculated when needed, instead of on initialization. This decreases the classical overhead by over 20%. Also,par_info
,obs_sharing_wires
, andobs_sharing_wires_id
are now public attributes. (#5696)The
qml.data
module now supports PyTree data types as dataset attributes (#5732)qml.ops.Conditional
now inherits fromqml.ops.SymbolicOp
, thus it inherits several useful common functionalities. Other properties such as adjoint and diagonalizing gates have been added using thebase
properties. (##5772)New dispatches for
qml.ops.Conditional
andqml.MeasurementValue
have been added toqml.equal
. (##5772)The
qml.snapshots
transform now supports arbitrary devices by running a separate tape for each snapshot for unsupported devices. (#5805)The
qml.Snapshot
operator now accepts sample-based measurements for finite-shot devices. (#5805)Device preprocess transforms now happen inside the ML boundary. (#5791)
Transforms applied to callables now use
functools.wraps
to preserve the docstring and call signature of the original function. (#5857)qml.qsvt()
now supports JAX arrays with angle conversions. (#5853)The sorting order of parameter-shift terms is now guaranteed to resolve ties in the absolute value with the sign of the shifts. (#5583)
Breaking changes ๐
Passing
shots
as a keyword argument to aQNode
initialization now raises an error instead of ignoring the input. (#5748)A custom decomposition can no longer be provided to
qml.QDrift
. Instead, apply the operations in your custom operation directly withqml.apply
. (#5698)Sampling observables composed of
X
,Y
,Z
andHadamard
now returns values of typefloat
instead ofint
. (#5607)qml.is_commuting
no longer accepts thewire_map
argument, which does not bring any functionality. (#5660)qml.from_qasm_file
has been removed. The user can open files and load their content usingqml.from_qasm
. (#5659)qml.load
has been removed in favour of more specific functions, such asqml.from_qiskit
, etc. (#5654)qml.transforms.convert_to_numpy_parameters
is now a proper transform and its output signature has changed, returning a list ofQuantumScript
s and a post-processing function instead of simply the transformed circuit. (#5693)Controlled.wires
does not includeself.work_wires
anymore. That can be accessed separately throughControlled.work_wires
. Consequently,Controlled.active_wires
has been removed in favour of the more commonControlled.wires
. (#5728)
Deprecations ๐
The
simplify
argument inqml.Hamiltonian
andqml.ops.LinearCombination
has been deprecated. Instead,qml.simplify()
can be called on the constructed operator. (#5677)qml.transforms.map_batch_transform
has been deprecated, since a transform can be applied directly to a batch of tapes. (#5676)The default behaviour of
qml.from_qasm()
to remove measurements in the QASM code has been deprecated. Usemeasurements=[]
to keep this behaviour ormeasurements=None
to keep the measurements from the QASM code. (#5882) (#5904)
Documentation ๐
The
qml.qchem
docs have been updated to showcase the new improvements. (#5758) (#5638)Several links to other functions in measurement process docstrings have been fixed. (#5913)
Information about mid-circuit measurements has been moved from the measurements quickstart page to its own mid-circuit measurements quickstart page (#5870)
The documentation for the
default.tensor
device has been added. (#5719)A small typo was fixed in the docstring for
qml.sample
. (#5685)Typesetting for some of the documentation was fixed, (use of left/right delimiters, fractions, and fixing incorrectly set up commands) (#5804)
The
qml.Tracker
examples have been updated. (#5803)The input types for
coupling_map
inqml.transpile
have been updated to reflect all the allowed input types bynx.to_networkx_graph
. (#5864)The text in the
qml.data
module and datasets quickstart has been slightly modified to lead to the quickstart first and highlightlist_datasets
. (5484)
Bug fixes ๐
qml.compiler.active
first checks whether Catalyst is imported at all to avoid changingjax_enable_x64
on module initialization. (#5960)The
__invert__
dunder method of theMeasurementValue
class uses an array-valued function. (#5955)Skip
Projector
-measurement tests on devices that do not support it. (#5951)The
default.tensor
device now preserves the order of wires if the initial MPS is created from a dense state vector. (#5892)Fixed a bug where
hadamard_grad
returned a wrong shape forqml.probs()
without wires. (#5860)An error is now raised on processing an
AnnotatedQueue
into aQuantumScript
if the queue contains something other than anOperator
,MeasurementProcess
, orQuantumScript
. (#5866)Fixed a bug in the wire handling on special controlled ops. (#5856)
Fixed a bug where
Sum
โs with repeated identical operations ended up with the same hash asSum
โs with different numbers of repeats. (#5851)qml.qaoa.cost_layer
andqml.qaoa.mixer_layer
can now be used withSum
operators. (#5846)Fixed a bug where
qml.MottonenStatePreparation
produces wrong derivatives at special parameter values. (#5774)Fixed a bug where fractional powers and adjoints of operators were commuted, which is not well-defined/correct in general. Adjoints of fractional powers can no longer be evaluated. (#5835)
qml.qnn.TorchLayer
now works with tuple returns. (#5816)An error is now raised if a transform is applied to a catalyst qjit object. (#5826)
qml.qnn.KerasLayer
andqml.qnn.TorchLayer
no longer mutate the inputqml.QNode
โs interface. (#5800)Docker builds on PR merging has been disabled. (#5777)
The validation of the adjoint method in
DefaultQubit
correctly handles device wires now. (#5761)QuantumPhaseEstimation.map_wires
on longer modifies the original operation instance. (#5698)The decomposition of
qml.AmplitudeAmplification
now correctly queues all operations. (#5698)Replaced
semantic_version
withpackaging.version.Version
, since the former cannot handle the metadata.post
in the version string. (#5754)The
dynamic_one_shot
transform now has expanded support for thejax
andtorch
interfaces. (#5672)The decomposition of
StronglyEntanglingLayers
is now compatible with broadcasting. (#5716)qml.cond
can now be applied toControlledOp
operations when deferring measurements. (#5725)The legacy
Tensor
class can now handle aProjector
with abstract tracer input. (#5720)Fixed a bug that raised an error regarding expected versus actual
dtype
when usingJAX-JIT
on a circuit that returned samples of observables containing theqml.Identity
operator. (#5607)The signature of
CaptureMeta
objects (likeOperator
) now match the signature of the__init__
call. (#5727)Vanilla NumPy arrays are now used in
test_projector_expectation
to avoid differentiatingqml.Projector
with respect to the state attribute. (#5683)qml.Projector
is now compatible withjax.jit
. (#5595)Finite-shot circuits with a
qml.probs
measurement, both with awires
orop
argument, can now be compiled withjax.jit
. (#5619)param_shift
,finite_diff
,compile
,insert
,merge_rotations
, andtranspile
now all work with circuits with non-commuting measurements. (#5424) (#5681)A correction has been added to
qml.bravyi_kitaev
to call the correct function for aqml.FermiSentence
input. (#5671)Fixed a bug where
sum_expand
produces incorrect result dimensions when combined with shot vectors, multiple measurements, and parameter broadcasting. (#5702)Fixed a bug in
qml.math.dot
that raises an error when only one of the operands is a scalar. (#5702)qml.matrix
is now compatible with QNodes compiled byqml.qjit
. (#5753)qml.snapshots
raises an error when a measurement other thanqml.state
is requested fromdefault.qubit.legacy
instead of silently returning the statevector. (#5805)Fixed a bug where
default.qutrit
was falsely determined to be natively compatible withqml.snapshots
. (#5805)Fixed a bug where the measurement of a
qml.Snapshot
instance was not passed on during theqml.adjoint
andqml.ctrl
operations. (#5805)qml.CNOT
andqml.Toffoli
now have anarithmetic_depth
of1
, as they are controlled operations. (#5797)Fixed a bug where the gradient of
ControlledSequence
,Reflection
,AmplitudeAmplification
, andQubitization
was incorrect ondefault.qubit.legacy
withparameter_shift
. (#5806)Fixed a bug where
split_non_commuting
raises an error when the circuit contains measurements of observables that are not Pauli words. (#5827)The
simplify
method forqml.Exp
now returns an operator with the correct number of Trotter steps, i.e. equal to the one from the pre-simplified operator. (#5831)Fixed a bug where
CompositeOp.overlapping_ops
would put overlapping operators in different groups, leading to incorrect results returned byLinearCombination.eigvals()
. (#5847)The correct decomposition for a
qml.PauliRot
with an identity aspauli_word
has been implemented, i.e. returns aqml.GlobalPhase
with half the angle. (#5875)qml.pauli_decompose
now works in a jit-ted context, such asjax.jit
andqml.qjit
. (#5878)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Tarun Kumar Allamsetty, Guillermo Alonso-Linaje, Utkarsh Azad, Lillian M. A. Frederiksen, Ludmila Botelho, Gabriel Bottrill, Thomas Bromley, Jack Brown, Astral Cai, Ahmed Darwish, Isaac De Vlugt, Diksha Dhawan, Pietropaolo Frisoni, Emiliano Godinez, Diego Guala, Daria Van Hende, Austin Huang, David Ittah, Soran Jahangiri, Rohan Jain, Mashhood Khan, Korbinian Kottmann, Christina Lee, Vincent Michaud-Rioux, Lee James OโRiordan, Mudit Pandey, Kenya Sakka, Jay Soni, Kazuki Tsuoka, Haochen Paul Wang, David Wierichs.
- orphan
Release 0.36.0ยถ
New features since last release
Estimate errors in a quantum circuit ๐งฎ
This version of PennyLane lays the foundation for estimating the total error in a quantum circuit from the combination of individual gate errors. (#5154) (#5464) (#5465) (#5278) (#5384)
Two new user-facing classes enable calculating and propagating gate errors in PennyLane:
qml.resource.SpectralNormError
: the spectral norm error is defined as the distance, in spectral norm, between the true unitary we intend to apply and the approximate unitary that is actually applied.qml.resource.ErrorOperation
: a base class that inherits fromqml.operation.Operation
and represents quantum operations which carry some form of algorithmic error.
SpectralNormError
can be used for back-of-the-envelope type calculations like obtaining the spectral norm error between two unitaries viaget_error
:import pennylane as qml from pennylane.resource import ErrorOperation, SpectralNormError intended_op = qml.RY(0.40, 0) actual_op = qml.RY(0.41, 0) # angle of rotation is slightly off
>>> SpectralNormError.get_error(intended_op, actual_op) 0.004999994791668309
SpectralNormError
is also a key tool to specify errors in larger quantum circuits:For operations representing a major building block of an algorithm, we can create a custom operation that inherits from
ErrorOperation
. This child class must override theerror
method and should return aSpectralNormError
instance:class MyErrorOperation(ErrorOperation): def __init__(self, error_val, wires): self.error_val = error_val super().__init__(wires=wires) def error(self): return SpectralNormError(self.error_val)
In this toy example,
MyErrorOperation
introduces an arbitrarySpectralNormError
when called in a QNode. It does not require a decomposition or matrix representation when used withnull.qubit
(suggested for use with resource and error estimation since circuit executions are not required to calculate resources or errors).dev = qml.device("null.qubit") @qml.qnode(dev) def circuit(): MyErrorOperation(0.1, wires=0) MyErrorOperation(0.2, wires=1) return qml.state()
The total spectral norm error of the circuit can be calculated using
qml.specs
:>>> qml.specs(circuit)()['errors'] {'SpectralNormError': SpectralNormError(0.30000000000000004)}
PennyLane already includes a number of built-in building blocks for algorithms like
QuantumPhaseEstimation
andTrotterProduct
.TrotterProduct
now propagates errors based on the number of steps performed in the Trotter product.QuantumPhaseEstimation
now propagates errors based on the error of its input unitary.dev = qml.device('null.qubit') hamiltonian = qml.dot([1.0, 0.5, -0.25], [qml.X(0), qml.Y(0), qml.Z(0)]) @qml.qnode(dev) def circuit(): qml.TrotterProduct(hamiltonian, time=0.1, order=2) qml.QuantumPhaseEstimation(MyErrorOperation(0.01, wires=0), estimation_wires=[1, 2, 3]) return qml.state()
Again, the total spectral norm error of the circuit can be calculated using
qml.specs
:>>> qml.specs(circuit)()["errors"] {'SpectralNormError': SpectralNormError(0.07616666666666666)}
Check out our error propagation demo to see how to use these new features in a real-world example!
Access an extended arsenal of quantum algorithms ๐น
The Fast Approximate BLock-Encodings (FABLE) algorithm for embedding a matrix into a quantum circuit as outlined in arXiv:2205.00081 is now accessible via the
qml.FABLE
template. (#5107)The usage of
qml.FABLE
is similar toqml.BlockEncode
but provides a more efficient circuit construction at the cost of a user-defined approximation level,tol
. The number of wires thatqml.FABLE
operates on is2*n + 1
, wheren
defines the dimension of the \(2^n \times 2^n\) matrix that we want to block-encode.import numpy as np A = np.array([[0.1, 0.2], [0.3, 0.4]]) dev = qml.device('default.qubit', wires=3) @qml.qnode(dev) def circuit(): qml.FABLE(A, tol = 0.001, wires=range(3)) return qml.state()
>>> mat = qml.matrix(circuit)() >>> 2 * mat[0:2, 0:2] array([[0.1+0.j, 0.2+0.j], [0.3+0.j, 0.4+0.j]])
A high-level interface for amplitude amplification and its variants is now available via the new
qml.AmplitudeAmplification
template. (#5160)Based on arXiv:quant-ph/0005055, given a state \(\vert \Psi \rangle = \alpha \vert \phi \rangle + \beta \vert \phi^{\perp} \rangle\),
qml.AmplitudeAmplification
amplifies the amplitude of \(\vert \phi \rangle\).Hereโs an example with a target state \(\vert \phi \rangle = \vert 2 \rangle = \vert 010 \rangle\), an input state \(\vert \Psi \rangle = H^{\otimes 3} \vert 000 \rangle\), as well as an oracle that flips the sign of \(\vert \phi \rangle\) and does nothing to \(\vert \phi^{\perp} \rangle\), which can be achieved in this case through
qml.FlipSign
.@qml.prod def generator(wires): for wire in wires: qml.Hadamard(wires=wire) U = generator(wires=range(3)) O = qml.FlipSign(2, wires=range(3))
Here,
U
is a quantum operation that is created by decorating a quantum function with@qml.prod
. This could alternatively be done by creating a user-defined custom operation with a decomposition. Amplitude amplification can then be set up within a circuit:dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(): generator(wires=range(3)) # prepares |Psi> = U|0> qml.AmplitudeAmplification(U, O, iters=10) return qml.probs(wires=range(3))
>>> print(np.round(circuit(), 3)) [0.01 0.01 0.931 0.01 0.01 0.01 0.01 0.01 ]
As expected, we amplify the \(\vert 2 \rangle\) state.
Reflecting about a given quantum state is now available via
qml.Reflection
. This operation is very useful in the amplitude amplification algorithm and offers a generalization ofqml.FlipSign
, which operates on basis states. (#5159)qml.Reflection
works by providing an operation, \(U\), that prepares the desired state, \(\vert \psi \rangle\), that we want to reflect about. In other words, \(U\) is such that \(U \vert 0 \rangle = \vert \psi \rangle\). In PennyLane, \(U\) must be anOperator
.For example, if we want to reflect about \(\vert \psi \rangle = \vert + \rangle\), then \(U = H\):
U = qml.Hadamard(wires=0) dev = qml.device('default.qubit') @qml.qnode(dev) def circuit(): qml.Reflection(U) return qml.state()
>>> circuit() tensor([0.-6.123234e-17j, 1.+6.123234e-17j], requires_grad=True)
Performing qubitization is now easily accessible with the new
qml.Qubitization
operator. (#5500)qml.Qubitization
encodes a Hamiltonian into a suitable unitary operator. When applied in conjunction with quantum phase estimation (QPE), it allows for computing the eigenvalue of an eigenvector of the given Hamiltonian.H = qml.dot([0.1, 0.3, -0.3], [qml.Z(0), qml.Z(1), qml.Z(0) @ qml.Z(2)]) @qml.qnode(qml.device("default.qubit")) def circuit(): # initialize the eigenvector qml.PauliX(2) # apply QPE measurements = qml.iterative_qpe( qml.Qubitization(H, control = [3,4]), ancilla = 5, iters = 3 ) return qml.probs(op = measurements)
Make use of more methods to map from molecules ๐บ๏ธ
A new function called
qml.bravyi_kitaev
has been added to perform the Bravyi-Kitaev mapping of fermionic Hamiltonians to qubit Hamiltonians. (#5390)This function presents an alternative mapping to
qml.jordan_wigner
orqml.parity_transform
which can help us measure expectation values more efficiently on hardware. Simply provide a fermionic Hamiltonian (created fromfrom_string
,FermiA
,FermiC
,FermiSentence
, orFermiWord
) and the number of qubits / spin orbitals in the system,n
:>>> fermi_ham = qml.fermi.from_string('0+ 1+ 1- 0-') >>> qubit_ham = qml.bravyi_kitaev(fermi_ham, n=6, tol=0.0) >>> print(qubit_ham) 0.25 * I(0) + -0.25 * Z(0) + -0.25 * (Z(0) @ Z(1)) + 0.25 * Z(1)
The
qml.qchem.hf_state
function has been upgraded to be compatible withqml.parity_transform
and the new Bravyi-Kitaev mapping (qml.bravyi_kitaev
). (#5472) (#5472)>>> state_bk = qml.qchem.hf_state(2, 6, basis="bravyi_kitaev") >>> print(state_bk) [1 0 0 0 0 0] >>> state_parity = qml.qchem.hf_state(2, 6, basis="parity") >>> print(state_parity) [1 0 0 0 0 0]
Calculate dynamical Lie algebras ๐พ
The dynamical Lie algebra (DLA) of a set of operators captures the range of unitary evolutions that the operators can generate. In v0.36 of PennyLane, we have added support for calculating important DLA concepts including:
A new
qml.lie_closure
function to compute the Lie closure of a list of operators, providing one way to obtain the DLA. (#5161) (#5169) (#5627)For a list of operators
ops = [op1, op2, op3, ..]
, one computes all nested commutators betweenops
until no new operators are generated from commutation. All these operators together form the DLA, see e.g. section IIB of arXiv:2308.01432.Take for example the following operators:
from pennylane import X, Y, Z ops = [X(0) @ X(1), Z(0), Z(1)]
A first round of commutators between all elements yields the new operators
Y(0) @ X(1)
andX(0) @ Y(1)
(omitting scalar prefactors).>>> qml.commutator(X(0) @ X(1), Z(0)) -2j * (Y(0) @ X(1)) >>> qml.commutator(X(0) @ X(1), Z(1)) -2j * (X(0) @ Y(1))
A next round of commutators between all elements further yields the new operator
Y(0) @ Y(1)
.>>> qml.commutator(X(0) @ Y(1), Z(0)) -2j * (Y(0) @ Y(1))
After that, no new operators emerge from taking nested commutators and we have the resulting DLA. This can now be done in short via
qml.lie_closure
as follows.>>> ops = [X(0) @ X(1), Z(0), Z(1)] >>> dla = qml.lie_closure(ops) >>> dla [X(0) @ X(1), Z(0), Z(1), -1.0 * (Y(0) @ X(1)), -1.0 * (X(0) @ Y(1)), -1.0 * (Y(0) @ Y(1))]
Computing the structure constants (the adjoint representation) of a dynamical Lie algebra. (5406)
For example, we can compute the adjoint representation of the transverse field Ising model DLA.
>>> dla = [X(0) @ X(1), Z(0), Z(1), Y(0) @ X(1), X(0) @ Y(1), Y(0) @ Y(1)] >>> structure_const = qml.structure_constants(dla) >>> structure_const.shape (6, 6, 6)
Visit the documentation of qml.structure_constants to understand how structure constants are a useful way to represent a DLA.
Computing the center of a dynamical Lie algebra. (#5477)
Given a DLA
g
, we can now compute its centre. Thecenter
is the collection of operators that commute with all other operators in the DLA.>>> g = [X(0), X(1) @ X(0), Y(1), Z(1) @ X(0)] >>> qml.center(g) [X(0)]
To help explain these concepts, check out the dynamical Lie algebras demo.
Improvements ๐
Simulate mixed-state qutrit systems
Mixed qutrit states can now be simulated with the
default.qutrit.mixed
device. (#5495) (#5451) (#5186) (#5082) (#5213)Thanks to contributors from the University of British Columbia, a mixed-state qutrit device is now available for simulation, providing a noise-capable equivalent to
default.qutrit
.dev = qml.device("default.qutrit.mixed") def circuit(): qml.TRY(0.1, wires=0) @qml.qnode(dev) def shots_circuit(): circuit() return qml.sample(), qml.expval(qml.GellMann(wires=0, index=1)) @qml.qnode(dev) def density_matrix_circuit(): circuit() return qml.state()
>>> shots_circuit(shots=5) (array([0, 0, 0, 0, 0]), 0.19999999999999996) >>> density_matrix_circuit() tensor([[0.99750208+0.j, 0.04991671+0.j, 0. +0.j], [0.04991671+0.j, 0.00249792+0.j, 0. +0.j], [0. +0.j, 0. +0.j, 0. +0.j]], requires_grad=True)
However, thereโs one crucial ingredient that we still need to add: support for qutrit noise operations. Keep your eyes peeled for this to arrive in the coming releases!
Work easily and efficiently with operators
This release completes the main phase of PennyLaneโs switchover to an updated approach for handling arithmetic operations between operators. The new approach is now enabled by default and is intended to realize a few objectives:
To make it as easy to work with PennyLane operators as it would be with pen and paper.
To improve the efficiency of operator arithmetic.
In many cases, this update should not break code. If issues do arise, check out the updated operator troubleshooting page and donโt hesitate to reach out to us on the PennyLane discussion forum. As a last resort the old behaviour can be enabled by calling
qml.operation.disable_new_opmath()
, but this is not recommended because support will not continue in future PennyLane versions (v0.36 and higher). (#5269)A new class called
qml.ops.LinearCombination
has been introduced. In essence, this class is an updated equivalent of the now-deprecatedqml.ops.Hamiltonian
but for usage with the new operator arithmetic. (#5216)qml.ops.Sum
now supports storing grouping information. Grouping type and method can be specified during construction using thegrouping_type
andmethod
keyword arguments ofqml.dot
,qml.sum
, orqml.ops.Sum
. The grouping indices are stored inSum.grouping_indices
. (#5179)a = qml.X(0) b = qml.prod(qml.X(0), qml.X(1)) c = qml.Z(0) obs = [a, b, c] coeffs = [1.0, 2.0, 3.0] op = qml.dot(coeffs, obs, grouping_type="qwc")
>>> op.grouping_indices ((2,), (0, 1))
Additionally,
grouping_type
andmethod
can be set or changed after construction usingSum.compute_grouping()
:a = qml.X(0) b = qml.prod(qml.X(0), qml.X(1)) c = qml.Z(0) obs = [a, b, c] coeffs = [1.0, 2.0, 3.0] op = qml.dot(coeffs, obs)
>>> op.grouping_indices is None True >>> op.compute_grouping(grouping_type="qwc") >>> op.grouping_indices ((2,), (0, 1))
Note that the grouping indices refer to the lists returned by
Sum.terms()
, notSum.operands
.A new function called
qml.operation.convert_to_legacy_H
that convertsSum
,SProd
, andProd
toHamiltonian
instances has been added. This function is intended for developers and will be removed in a future release without a deprecation cycle. (#5309)The
qml.is_commuting
function now acceptsSum
,SProd
, andProd
instances. (#5351)Operators can now be left-multiplied by NumPy arrays (i.e.,
arr * op
). (#5361)op.generator()
, whereop
is anOperator
instance, now returns operators consistent with the global setting forqml.operator.active_new_opmath()
wherever possible.Sum
,SProd
andProd
instances will be returned even after disabling the new operator arithmetic in cases where they offer additional functionality not available using legacy operators. (#5253) (#5410) (#5411) (#5421)Prod
instances temporarily have a newobs
property, which helps smoothen the transition of the new operator arithmetic system. In particular, this is aimed at preventing breaking code that usesTensor.obs
. The property has been immediately deprecated. Moving forward, we recommend usingop.operands
. (#5539)qml.ApproxTimeEvolution
is now compatible with any operator that has a definedpauli_rep
. (#5362)Hamiltonian.pauli_rep
is now defined if the Hamiltonian is a linear combination of Pauli operators. (#5377)Prod
instances created with qutrit operators now have a definedeigvals()
method. (#5400)qml.transforms.hamiltonian_expand
andqml.transforms.sum_expand
can now handle multi-term observables with a constant offset (i.e., terms likeqml.I()
). (#5414) (#5543)qml.qchem.taper_operation
is now compatible with the new operator arithmetic. (#5326)The warning for an observable that might not be hermitian in QNode executions has been removed. This enables jit-compilation. (#5506)
qml.transforms.split_non_commuting
will now work with single-term operator arithmetic. (#5314)LinearCombination
andSum
now accept_grouping_indices
on initialization. This addition is relevant to developers only. (#5524)Calculating the dense, differentiable matrix for
PauliSentence
and operators with Pauli sentences is now faster. (#5578)
Community contributions ๐ฅณ
ExpectationMP
,VarianceMP
,CountsMP
, andSampleMP
now have aprocess_counts
method (similar toprocess_samples
). This allows for calculating measurements given acounts
dictionary. (#5256) (#5395)Type-hinting has been added in the
Operator
class for better interpretability. (#5490)An alternate strategy for sampling with multiple different
shots
values has been implemented via theshots.bins()
method, which samples all shots at once and then processes each separately. (#5476)
Mid-circuit measurements and dynamic circuits
A new module called
qml.capture
that will contain PennyLaneโs own capturing mechanism for hybrid quantum-classical programs has been added. (#5509)The
dynamic_one_shot
transform has been introduced, enabling dynamic circuit execution on circuits with finiteshots
and devices that natively support mid-circuit measurements. (#5266)The
QubitDevice
class and children classes support thedynamic_one_shot
transform provided that they support mid-circuit measurement operations natively. (#5317)default.qubit
can now be provided a random seed for sampling mid-circuit measurements with finite shots. This (1) ensures that random behaviour is more consistent withdynamic_one_shot
anddefer_measurements
and (2) makes our continuous-integration (CI) have less failures due to stochasticity. (#5337)
Performance and broadcasting
Gradient transforms may now be applied to batched/broadcasted QNodes as long as the broadcasting is in non-trainable parameters. (#5452)
The performance of computing the matrix of
qml.QFT
has been improved. (#5351)qml.transforms.broadcast_expand
now supports shot vectors when returningqml.sample()
. (#5473)LightningVJPs
is now compatible with Lightning devices using the new device API. (#5469)
Device capabilities
Obtaining classical shadows using the
default.clifford
device is now compatible with stimv1.13.0
. (#5409)default.mixed
has improved support for sampling-based measurements with non-NumPy interfaces. (#5514) (#5530)default.mixed
now supports arbitrary state-based measurements withqml.Snapshot
. (#5552)null.qubit
has been upgraded to the new device API and has support for all measurements and various modes of differentiation. (#5211)
Other improvements
Entanglement entropy can now be calculated with
qml.math.vn_entanglement_entropy
, which computes the von Neumann entanglement entropy from a density matrix. A corresponding QNode transform,qml.qinfo.vn_entanglement_entropy
, has also been added. (#5306)qml.draw
andqml.draw_mpl
will now attempt to sort the wires if no wire order is provided by the user or the device. (#5576)A clear error message is added in
KerasLayer
when using the newest version of TensorFlow with Keras 3 (which is not currently compatible withKerasLayer
), linking to instructions to enable Keras 2. (#5488)qml.ops.Conditional
now stores thedata
,num_params
, andndim_param
attributes of the operator it wraps. (#5473)The
molecular_hamiltonian
function callsPySCF
directly whenmethod='pyscf'
is selected. (#5118)cache_execute
has been replaced with an alternate implementation based on@transform
. (#5318)QNodes now defer
diff_method
validation to the device under the new device API. (#5176)The device test suite has been extended to cover gradient methods, templates and arithmetic observables. (#5273) (#5518)
A typo and string formatting mistake have been fixed in the error message for
ClassicalShadow._convert_to_pauli_words
when the input is not a validpauli_rep
. (#5572)Circuits running on
lightning.qubit
and that returnqml.state()
now preserve thedtype
when specified. (#5547)
Breaking changes ๐
qml.matrix()
called on the following will now raise an error ifwire_order
is not specified:single_tape_transform
,batch_transform
,qfunc_transform
,op_transform
,gradient_transform
andhessian_transform
have been removed. Instead, switch to using the newqml.transform
function. Please refer to the transform docs to see how this can be done. (#5339)Attempting to multiply
PauliWord
andPauliSentence
with*
will raise an error. Instead, use@
to conform with the PennyLane convention. (#5341)DefaultQubit
now uses a pre-emptive key-splitting strategy to avoid reusing JAX PRNG keys throughout a singleexecute
call. (#5515)qml.pauli.pauli_mult
andqml.pauli.pauli_mult_with_phase
have been removed. Instead, useqml.simplify(qml.prod(pauli_1, pauli_2))
to get the reduced operator. (#5324)>>> op = qml.simplify(qml.prod(qml.PauliX(0), qml.PauliZ(0))) >>> op -1j*(PauliY(wires=[0])) >>> [phase], [base] = op.terms() >>> phase, base (-1j, PauliY(wires=[0]))
The
dynamic_one_shot
transform now uses sampling (SampleMP
) to get back the values of the mid-circuit measurements. (#5486)Operator
dunder methods now combine like-operator arithmetic classes vialazy=False
. This reduces the chances of getting aRecursionError
and makes nested operators easier to work with. (#5478)The private functions
_pauli_mult
,_binary_matrix
and_get_pauli_map
from thepauli
module have been removed. The same functionality can be achieved using newer features in thepauli
module. (#5323)MeasurementProcess.name
andMeasurementProcess.data
have been removed. UseMeasurementProcess.obs.name
andMeasurementProcess.obs.data
instead. (#5321)Operator.validate_subspace(subspace)
has been removed. Instead, useqml.ops.qutrit.validate_subspace(subspace)
. (#5311)The contents of
qml.interfaces
has been moved insideqml.workflow
. The old import path no longer exists. (#5329)Since
default.mixed
does not support snapshots with measurements, attempting to do so will result in aDeviceError
instead of getting the density matrix. (#5416)LinearCombination._obs_data
has been removed. You can still useLinearCombination.compare
to check mathematical equivalence between aLinearCombination
and another operator. (#5504)
Deprecations ๐
Accessing
qml.ops.Hamiltonian
is deprecated because it points to the old version of the class that may not be compatible with the new approach to operator arithmetic. Instead, usingqml.Hamiltonian
is recommended because it dispatches to theLinearCombination
class when the new approach to operator arithmetic is enabled. This will allow you to continue to useqml.Hamiltonian
with existing code without needing to make any changes. (#5393)qml.load
has been deprecated. Instead, please use the functions outlined in the Importing workflows quickstart guide. (#5312)Specifying
control_values
with a bit string inqml.MultiControlledX
has been deprecated. Instead, use a list of booleans or 1s and 0s. (#5352)qml.from_qasm_file
has been deprecated. Instead, please open the file and then load its content usingqml.from_qasm
. (#5331)>>> with open("test.qasm", "r") as f: ... circuit = qml.from_qasm(f.read())
Documentation ๐
A new page explaining the shapes and nesting of return types has been added. (#5418)
Redundant documentation for the
evolve
function has been removed. (#5347)The final example in the
compile
docstring has been updated to use transforms correctly. (#5348)A link to the demos for using
qml.SpecialUnitary
andqml.QNGOptimizer
has been added to their respective docstrings. (#5376)A code example in the
qml.measure
docstring has been added that showcases returning mid-circuit measurement statistics from QNodes. (#5441)The computational basis convention used for
qml.measure
โ 0 and 1 rather than ยฑ1 โ has been clarified in its docstring. (#5474)A new Release news section has been added to the table of contents, containing release notes, deprecations, and other pages focusing on recent changes. (#5548)
A summary of all changes has been added in the โUpdated Operatorsโ page in the new โRelease newsโ section in the docs. (#5483) (#5636)
Bug fixes ๐
Patches the QNode so that parameter-shift will be considered best with lightning if
qml.metric_tensor
is in the transform program. (#5624)Stopped printing the ID of
qcut.MeasureNode
andqcut.PrepareNode
in tape drawing. (#5613)Improves the error message for setting shots on the new device interface, or trying to access a property that no longer exists. (#5616)
Fixed a bug where
qml.draw
andqml.draw_mpl
incorrectly raised errors for circuits collecting statistics on mid-circuit measurements while usingqml.defer_measurements
. (#5610)Using shot vectors with
param_shift(... broadcast=True)
caused a bug. This combination is no longer supported and will be added again in the next release. Fixed a bug with custom gradient recipes that only consist of unshifted terms. (#5612) (#5623)qml.counts
now returns the same keys withdynamic_one_shot
anddefer_measurements
. (#5587)null.qubit
now automatically supports any operation without a decomposition. (#5582)Fixed a bug where the shape and type of derivatives obtained by applying a gradient transform to a QNode differed based on whether the QNode uses classical coprocessing. (#4945)
ApproxTimeEvolution
,CommutingEvolution
,QDrift
, andTrotterProduct
now de-queue their input observable. (#5524)(In)equality of
qml.HilbertSchmidt
instances is now reported correctly byqml.equal
. (#5538)qml.ParticleConservingU1
andqml.ParticleConservingU2
no longer raise an error when the initial state is not specified but default to the all-zeros state. (#5535)qml.counts
no longer returns negative samples when measuring 8 or more wires. (#5544) (#5556)The
dynamic_one_shot
transform now works with broadcasting. (#5473)Diagonalizing gates are now applied when measuring
qml.probs
on non-computational basis states on a Lightning device. (#5529)two_qubit_decomposition
no longer diverges at a special case of a unitary matrix. (#5448)The
qml.QNSPSAOptimizer
now correctly handles optimization for legacy devices that do not follow the new device API. (#5497)Operators applied to all wires are now drawn correctly in a circuit with mid-circuit measurements. (#5501)
Fixed a bug where certain unary mid-circuit measurement expressions would raise an uncaught error. (#5480)
Probabilities now sum to 1 when using the
torch
interface withdefault_dtype
set totorch.float32
. (#5462)Tensorflow can now handle devices with
float32
results butfloat64
input parameters. (#5446)Fixed a bug where the
argnum
keyword argument ofqml.gradients.stoch_pulse_grad
references the wrong parameters in a tape, creating an inconsistency with other differentiation methods and preventing some use cases. (#5458)Bounded value failures due to numerical noise with calls to
np.random.binomial
is now avoided. (#5447)Using
@
with legacy Hamiltonian instances now properly de-queues the previously existing operations. (#5455)The
QNSPSAOptimizer
now properly handles differentiable parameters, resulting in being able to use it for more than one optimization step. (#5439)The QNode interface now resets if an error occurs during execution. (#5449)
Failing tests due to changes with Lightningโs adjoint diff pipeline have been fixed. (#5450)
Failures occurring when making autoray-dispatched calls to Torch with paired CPU data have been fixed. (#5438)
jax.jit
now works withqml.sample
with a multi-wire observable. (#5422)qml.qinfo.quantum_fisher
now works with non-default.qubit
devices. (#5423)We no longer perform unwanted
dtype
promotion in thepauli_rep
ofSProd
instances when using Tensorflow. (#5246)Fixed
TestQubitIntegration.test_counts
intests/interfaces/test_jax_qnode.py
to always produce counts for all outcomes. (#5336)Fixed
PauliSentence.to_mat(wire_order)
to support identities with wires. (#5407)CompositeOp.map_wires
now correctly maps theoverlapping_ops
property. (#5430)DefaultQubit.supports_derivatives
has been updated to correctly handle circuits containing mid-circuit measurements and adjoint differentiation. (#5434)SampleMP
,ExpectationMP
,CountsMP
, andVarianceMP
constructed witheigvals
can now properly process samples. (#5463)Fixed a bug in
hamiltonian_expand
that produces incorrect output dimensions when shot vectors are combined with parameter broadcasting. (#5494)default.qubit
now allows measuringIdentity
on no wires and observables containingIdentity
on no wires. (#5570)Fixed a bug where
TorchLayer
does not work with shot vectors. (#5492)Fixed a bug where the output shape of a QNode returning a list containing a single measurement is incorrect when combined with shot vectors. (#5492)
Fixed a bug in
qml.math.kron
that makes Torch incompatible with NumPy. (#5540)Fixed a bug in
_group_measurements
that fails to group measurements with commuting observables when they are operands ofProd
. (#5525)qml.equal
can now be used with sums and products that contain operators on no wires likeI
andGlobalPhase
. (#5562)CompositeOp.has_diagonalizing_gates
now does a more complete check of the base operators to ensure consistency betweenop.has_diagonalzing_gates
andop.diagonalizing_gates()
(#5603)Updated the
method
kwarg ofqml.TrotterProduct().error()
to be more clear that we are computing upper-bounds. (#5637)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Tarun Kumar Allamsetty, Guillermo Alonso, Mikhail Andrenkov, Utkarsh Azad, Gabriel Bottrill, Thomas Bromley, Astral Cai, Diksha Dhawan, Isaac De Vlugt, Amintor Dusko, Pietropaolo Frisoni, Lillian M. A. Frederiksen, Diego Guala, Austin Huang, Soran Jahangiri, Korbinian Kottmann, Christina Lee, Vincent Michaud-Rioux, Mudit Pandey, Kenya Sakka, Jay Soni, Matthew Silverman, David Wierichs.
- orphan
Release 0.35.0ยถ
New features since last release
Qiskit 1.0 integration ๐
This version of PennyLane makes it easier to import circuits from Qiskit. (#5218) (#5168)
The
qml.from_qiskit
function converts a Qiskit QuantumCircuit into a PennyLane quantum function. Althoughqml.from_qiskit
already exists in PennyLane, we have made a number of improvements to make importing from Qiskit easier. And yes โqml.from_qiskit
functionality is compatible with both Qiskit 1.0 and earlier versions! Hereโs a comprehensive list of the improvements:You can now append PennyLane measurements onto the quantum function returned by
qml.from_qiskit
. Consider this simple Qiskit circuit:import pennylane as qml from qiskit import QuantumCircuit qc = QuantumCircuit(2) qc.rx(0.785, 0) qc.ry(1.57, 1)
We can convert it into a PennyLane QNode in just a few lines, with PennyLane
measurements
easily included:>>> dev = qml.device("default.qubit") >>> measurements = qml.expval(qml.Z(0) @ qml.Z(1)) >>> qfunc = qml.from_qiskit(qc, measurements=measurements) >>> qnode = qml.QNode(qfunc, dev) >>> qnode() tensor(0.00056331, requires_grad=True)
Quantum circuits that already contain Qiskit-side measurements can be faithfully converted with
qml.from_qiskit
. Consider this example Qiskit circuit:qc = QuantumCircuit(3, 2) # Teleportation qc.rx(0.9, 0) # Prepare input state on qubit 0 qc.h(1) # Prepare Bell state on qubits 1 and 2 qc.cx(1, 2) qc.cx(0, 1) # Perform teleportation qc.h(0) qc.measure(0, 0) qc.measure(1, 1) with qc.if_test((1, 1)): # Perform first conditional qc.x(2)
This circuit can be converted into PennyLane with the Qiskit measurements still accessible. For example, we can use those results as inputs to a mid-circuit measurement in PennyLane:
@qml.qnode(dev) def teleport(): m0, m1 = qml.from_qiskit(qc)() qml.cond(m0, qml.Z)(2) return qml.density_matrix(2)
>>> teleport() tensor([[0.81080498+0.j , 0. +0.39166345j], [0. -0.39166345j, 0.18919502+0.j ]], requires_grad=True)
It is now more intuitive to handle and differentiate parametrized Qiskit circuits. Consider the following circuit:
from qiskit.circuit import Parameter from pennylane import numpy as np angle0 = Parameter("x") angle1 = Parameter("y") qc = QuantumCircuit(2, 2) qc.rx(angle0, 0) qc.ry(angle1, 1) qc.cx(1, 0)
We can convert this circuit into a QNode with two arguments, corresponding to
x
andy
:measurements = qml.expval(qml.PauliZ(0)) qfunc = qml.from_qiskit(qc, measurements) qnode = qml.QNode(qfunc, dev)
The QNode can be evaluated and differentiated:
>>> x, y = np.array([0.4, 0.5], requires_grad=True) >>> qnode(x, y) tensor(0.80830707, requires_grad=True) >>> qml.grad(qnode)(x, y) (tensor(-0.34174675, requires_grad=True), tensor(-0.44158016, requires_grad=True))
This shows how easy it is to make a Qiskit circuit differentiable with PennyLane.
In addition to circuits, it is also possible to convert operators from Qiskit to PennyLane with a new function called
qml.from_qiskit_op
. (#5251)A Qiskit SparsePauliOp can be converted to a PennyLane operator using
qml.from_qiskit_op
:>>> from qiskit.quantum_info import SparsePauliOp >>> qiskit_op = SparsePauliOp(["II", "XY"]) >>> qiskit_op SparsePauliOp(['II', 'XY'], coeffs=[1.+0.j, 1.+0.j]) >>> pl_op = qml.from_qiskit_op(qiskit_op) >>> pl_op I(0) + X(1) @ Y(0)
Combined with
qml.from_qiskit
, it becomes easy to quickly calculate quantities like expectation values by converting the whole workflow to PennyLane:qc = QuantumCircuit(2) # Create circuit qc.rx(0.785, 0) qc.ry(1.57, 1) measurements = qml.expval(pl_op) # Create QNode qfunc = qml.from_qiskit(qc, measurements) qnode = qml.QNode(qfunc, dev)
>>> qnode() # Evaluate! tensor(0.29317504, requires_grad=True)
Native mid-circuit measurements on Default Qubit ๐ก
Mid-circuit measurements can now be more scalable and efficient in finite-shots mode with
default.qubit
by simulating them in a similar way to what happens on quantum hardware. (#5088) (#5120)Previously, mid-circuit measurements (MCMs) would be automatically replaced with an additional qubit using the
@qml.defer_measurements
transform. The circuit below would have required thousands of qubits to simulate.Now, MCMs are performed in a similar way to quantum hardware with finite shots on
default.qubit
. For each shot and each time an MCM is encountered, the device evaluates the probability of projecting onto|0>
or|1>
and makes a random choice to collapse the circuit state. This approach works well when there are a lot of MCMs and the number of shots is not too high.import pennylane as qml dev = qml.device("default.qubit", shots=10) @qml.qnode(dev) def f(): for i in range(1967): qml.Hadamard(0) qml.measure(0) return qml.sample(qml.PauliX(0))
>>> f() tensor([-1, -1, -1, 1, 1, -1, 1, -1, 1, -1], requires_grad=True)
Work easily and efficiently with operators ๐ง
Over the past few releases, PennyLaneโs approach to operator arithmetic has been in the process of being overhauled. We have a few objectives:
To make it as easy to work with PennyLane operators as it would be with pen and paper.
To improve the efficiency of operator arithmetic.
The updated operator arithmetic functionality is still being finalized, but can be activated using
qml.operation.enable_new_opmath()
. In the next release, the new behaviour will become the default, so we recommend enabling now to become familiar with the new system!The following updates have been made in this version of PennyLane:
You can now easily access Pauli operators via
I
,X
,Y
, andZ
: (#5116)>>> from pennylane import I, X, Y, Z >>> X(0) X(0)
The original long-form names
Identity
,PauliX
,PauliY
, andPauliZ
remain available, but use of the short-form names is now recommended.The original long-form names
Identity
,PauliX
,PauliY
, andPauliZ
remain available, but use of the short-form names is now recommended.A new
qml.commutator
function is now available that allows you to compute commutators between PennyLane operators. (#5051) (#5052) (#5098)>>> qml.commutator(X(0), Y(0)) 2j * Z(0)
Operators in PennyLane can have a backend Pauli representation, which can be used to perform faster operator arithmetic. Now, the Pauli representation will be automatically used for calculations when available. (#4989) (#5001) (#5003) (#5017) (#5027)
The Pauli representation can be optionally accessed via
op.pauli_rep
:>>> qml.operation.enable_new_opmath() >>> op = X(0) + Y(0) >>> op.pauli_rep 1.0 * X(0) + 1.0 * Y(0)
Extensive improvements have been made to the string representations of PennyLane operators, making them shorter and possible to copy-paste as valid PennyLane code. (#5116) (#5138)
>>> 0.5 * X(0) 0.5 * X(0) >>> 0.5 * (X(0) + Y(1)) 0.5 * (X(0) + Y(1))
Sums with many terms are broken up into multiple lines, but can still be copied back as valid code:
>>> 0.5 * (X(0) @ X(1)) + 0.7 * (X(1) @ X(2)) + 0.8 * (X(2) @ X(3)) ( 0.5 * (X(0) @ X(1)) + 0.7 * (X(1) @ X(2)) + 0.8 * (X(2) @ X(3)) )
Linear combinations of operators and operator multiplication via
Sum
andProd
, respectively, have been updated to reach feature parity withHamiltonian
andTensor
, respectively. This should minimize the effort to port over any existing code. (#5070) (#5132) (#5133)Updates include support for grouping via the
pauli
module:>>> obs = [X(0) @ Y(1), Z(0), Y(0) @ Z(1), Y(1)] >>> qml.pauli.group_observables(obs) [[Y(0) @ Z(1)], [X(0) @ Y(1), Y(1)], [Z(0)]]
New Clifford device ๐ฆพ
A new
default.clifford
device enables efficient simulation of large-scale Clifford circuits defined in PennyLane through the use of stim as a backend. (#4936) (#4954) (#5144)Given a circuit with only Clifford gates, one can use this device to obtain the usual range of PennyLane measurements as well as the state represented in the Tableau form of Aaronson & Gottesman (2004):
import pennylane as qml dev = qml.device("default.clifford", tableau=True) @qml.qnode(dev) def circuit(): qml.CNOT(wires=[0, 1]) qml.PauliX(wires=[1]) qml.ISWAP(wires=[0, 1]) qml.Hadamard(wires=[0]) return qml.state()
>>> circuit() array([[0, 1, 1, 0, 0], [1, 0, 1, 1, 1], [0, 0, 0, 1, 0], [1, 0, 0, 1, 1]])
The
default.clifford
device also supports thePauliError
,DepolarizingChannel
,BitFlip
andPhaseFlip
noise channels when operating in finite-shot mode.
Improvements ๐
Faster gradients with VJPs and other performance improvements
Vector-Jacobian products (VJPs) can result in faster computations when the output of your quantum Node has a low dimension. They can be enabled by setting
device_vjp=True
when loading a QNode. In the next release of PennyLane, VJPs are planned to be used by default, when available.In this release, we have unlocked:
Adjoint device VJPs can be used with
jax.jacobian
, meaning thatdevice_vjp=True
is always faster when using JAX withdefault.qubit
. (#4963)PennyLane can now use lightning-provided VJPs. (#4914)
VJPs can be used with TensorFlow, though support has not yet been added for
tf.Function
and Tensorflow Autograph. (#4676)
Measuring
qml.probs
is now faster due to an optimization in converting samples to counts. (#5145)The performance of circuit-cutting workloads with large numbers of generated tapes has been improved. (#5005)
Queueing (
AnnotatedQueue
) has been removed fromqml.cut_circuit
andqml.cut_circuit_mc
to improve performance for large workflows. (#5108)
Community contributions ๐ฅณ
A new function called
qml.fermi.parity_transform
has been added for parity mapping of a fermionic Hamiltonian. (#4928)It is now possible to transform a fermionic Hamiltonian to a qubit Hamiltonian with parity mapping.
import pennylane as qml fermi_ham = qml.fermi.FermiWord({(0, 0) : '+', (1, 1) : '-'}) qubit_ham = qml.fermi.parity_transform(fermi_ham, n=6)
>>> print(qubit_ham) -0.25j * Y(0) + (-0.25+0j) * (X(0) @ Z(1)) + (0.25+0j) * X(0) + 0.25j * (Y(0) @ Z(1))
The transform
split_non_commuting
now accepts measurements of typeprobs
,sample
, andcounts
, which accept both wires and observables. (#4972)The efficiency of matrix calculations when an operator is symmetric over a given set of wires has been improved. (#3601)
The
pennylane/math/quantum.py
module now has support for computing the minimum entropy of a density matrix. (#3959)>>> x = [1, 0, 0, 1] / np.sqrt(2) >>> x = qml.math.dm_from_state_vector(x) >>> qml.math.min_entropy(x, indices=[0]) 0.6931471805599455
A function called
apply_operation
that applies operations to device-compatible states has been added to the newqutrit_mixed
module found inqml.devices
. (#5032)A function called
measure
has been added to the newqutrit_mixed
module found inqml.devices
that measures device-compatible states for a collection of measurement processes. (#5049)A
partial_trace
function has been added toqml.math
for taking the partial trace of matrices. (#5152)
Other operator arithmetic improvements
The following capabilities have been added for Pauli arithmetic: (#4989) (#5001) (#5003) (#5017) (#5027) (#5018)
You can now multiply
PauliWord
andPauliSentence
instances by scalars (e.g.,0.5 * PauliWord({0: "X"})
or0.5 * PauliSentence({PauliWord({0: "X"}): 1.})
).You can now intuitively add and subtract
PauliWord
andPauliSentence
instances and scalars together (scalars are treated implicitly as multiples of the identity,I
). For example,ps1 + pw1 + 1.
for some Pauli wordpw1 = PauliWord({0: "X", 1: "Y"})
and Pauli sentenceps1 = PauliSentence({pw1: 3.})
.You can now element-wise multiply
PauliWord
,PauliSentence
, and operators together withqml.dot
(e.g.,qml.dot([0.5, -1.5, 2], [pw1, ps1, id_word])
withid_word = PauliWord({})
).qml.matrix
now acceptsPauliWord
andPauliSentence
instances (e.g.,qml.matrix(PauliWord({0: "X"}))
).It is now possible to compute commutators with Pauli operators natively with the new
commutator
method.>>> op1 = PauliWord({0: "X", 1: "X"}) >>> op2 = PauliWord({0: "Y"}) + PauliWord({1: "Y"}) >>> op1.commutator(op2) 2j * Z(0) @ X(1) + 2j * X(0) @ Z(1)
Composite operations (e.g., those made with
qml.prod
andqml.sum
) and scalar-product operations convertHamiltonian
andTensor
operands toSum
andProd
types, respectively. This helps avoid the mixing of incompatible operator types. (#5031) (#5063)qml.Identity()
can be initialized without wires. Measuring it is currently not possible, though. (#5106)qml.dot
now returns aSum
class even when all the coefficients match. (#5143)qml.pauli.group_observables
now supports groupingProd
andSProd
operators. (#5070)The performance of converting a
PauliSentence
to aSum
has been improved. (#5141) (#5150)Akin to
qml.Hamiltonian
features, the coefficients and operators that make up composite operators formed viaSum
orProd
can now be accessed with theterms()
method. (#5132) (#5133) (#5164)>>> qml.operation.enable_new_opmath() >>> op = X(0) @ (0.5 * X(1) + X(2)) >>> op.terms() ([0.5, 1.0], [X(1) @ X(0), X(2) @ X(0)])
String representations of
ParametrizedHamiltonian
have been updated to match the style of other PL operators. (#5215)
Other improvements
The
pl-device-test
suite is now compatible with theqml.devices.Device
interface. (#5229)The
QSVT
operation now determines itsdata
from the block encoding and projector operator data. (#5226) (#5248)The
BlockEncode
operator is now JIT-compatible with JAX. (#5110)The
qml.qsvt
function usesqml.GlobalPhase
instead ofqml.exp
to define a global phase. (#5105)The
tests/ops/functions/conftest.py
test has been updated to ensure that all operator types are tested for validity. (#4978)A new
pennylane.workflow
module has been added. This module now containsqnode.py
,execution.py
,set_shots.py
,jacobian_products.py
, and the submoduleinterfaces
. (#5023)A more informative error is now raised when calling
adjoint_jacobian
with trainable state-prep operations. (#5026)qml.workflow.get_transform_program
andqml.workflow.construct_batch
have been added to inspect the transform program and batch of tapes at different stages. (#5084)All custom controlled operations such as
CRX
,CZ
,CNOT
,ControlledPhaseShift
now inherit fromControlledOp
, giving them additional properties such ascontrol_wire
andcontrol_values
. Callingqml.ctrl
onRX
,RY
,RZ
,Rot
, andPhaseShift
with a single control wire will return gates of typesCRX
,CRY
, etc. as opposed to a generalControlled
operator. (#5069) (#5199)The CI will now fail if coverage data fails to upload to codecov. Previously, it would silently pass and the codecov check itself would never execute. (#5101)
qml.ctrl
called on operators with custom controlled versions will now return instances of the custom class, and it will flatten nested controlled operators to a single multi-controlled operation. ForPauliX
,CNOT
,Toffoli
, andMultiControlledX
, callingqml.ctrl
will always resolve to the best option inCNOT
,Toffoli
, orMultiControlledX
depending on the number of control wires and control values. (#5125)Unwanted warning filters have been removed from tests and no
PennyLaneDeprecationWarning
s are being raised unexpectedly. (#5122)New error tracking and propagation functionality has been added (#5115) (#5121)
The method
map_batch_transform
has been replaced with the method_batch_transform
implemented inTransformDispatcher
. (#5212)TransformDispatcher
can now dispatch onto a batch of tapes, making it easier to compose transforms when working in the tape paradigm. (#5163)qml.ctrl
is now a simple wrapper that either calls PennyLaneโs built increate_controlled_op
or uses the Catalyst implementation. (#5247)Controlled composite operations can now be decomposed using ZYZ rotations. (#5242)
New functions called
qml.devices.modifiers.simulator_tracking
andqml.devices.modifiers.single_tape_support
have been added to add basic default behavior onto a device class. (#5200)
Breaking changes ๐
Passing additional arguments to a transform that decorates a QNode must now be done through the use of
functools.partial
. (#5046)qml.ExpvalCost
has been removed. Users should useqml.expval()
moving forward. (#5097)Caching of executions is now turned off by default when
max_diff == 1
, as the classical overhead cost outweighs the probability that duplicate circuits exists. (#5243)The entry point convention registering compilers with PennyLane has changed. (#5140)
To allow for packages to register multiple compilers with PennyLane, the
entry_points
convention under the designated group namepennylane.compilers
has been modified.Previously, compilers would register
qjit
(JIT decorator),ops
(compiler-specific operations), andcontext
(for tracing and program capture).Now, compilers must register
compiler_name.qjit
,compiler_name.ops
, andcompiler_name.context
, wherecompiler_name
is replaced by the name of the provided compiler.For more information, please see the documentation on adding compilers.
PennyLane source code is now compatible with the latest version of
black
. (#5112) (#5119)gradient_analysis_and_validation
has been renamed tofind_and_validate_gradient_methods
. Instead of returning a list, it now returns a dictionary of gradient methods for each parameter index, and no longer mutates the tape. (#5035)Multiplying two
PauliWord
instances no longer returns a tuple(new_word, coeff)
but insteadPauliSentence({new_word: coeff})
. The old behavior is still available with the private methodPauliWord._matmul(other)
for faster processing. (#5045)Observable.return_type
has been removed. Instead, you should inspect the type of the surrounding measurement process. (#5044)ClassicalShadow.entropy()
no longer needs anatol
keyword as a better method to estimate entropies from approximate density matrix reconstructions (with potentially negative eigenvalues). (#5048)Controlled operators with a custom controlled version decompose like how their controlled counterpart decomposes as opposed to decomposing into their controlled version. (#5069) (#5125)
For example:
>>> qml.ctrl(qml.RX(0.123, wires=1), control=0).decomposition() [ RZ(1.5707963267948966, wires=[1]), RY(0.0615, wires=[1]), CNOT(wires=[0, 1]), RY(-0.0615, wires=[1]), CNOT(wires=[0, 1]), RZ(-1.5707963267948966, wires=[1]) ]
QuantumScript.is_sampled
andQuantumScript.all_sampled
have been removed. Users should now validate these properties manually. (#5072)qml.transforms.one_qubit_decomposition
andqml.transforms.two_qubit_decomposition
have been removed. Instead, you should useqml.ops.one_qubit_decomposition
andqml.ops.two_qubit_decomposition
. (#5091)
Deprecations ๐
Calling
qml.matrix
without providing awire_order
on objects where the wire order could be ambiguous now raises a warning. In the future, thewire_order
argument will be required in these cases. (#5039)Operator.validate_subspace(subspace)
has been relocated to theqml.ops.qutrit.parametric_ops
module and will be removed from the Operator class in an upcoming release. (#5067)Matrix and tensor products between
PauliWord
andPauliSentence
instances are done using the@
operator,*
will be used only for scalar multiplication. Note also the breaking change that the product of twoPauliWord
instances now returns aPauliSentence
instead of a tuple(new_word, coeff)
. (#4989) (#5054)MeasurementProcess.name
andMeasurementProcess.data
are now deprecated, as they contain dummy values that are no longer needed. (#5047) (#5071) (#5076) (#5122)qml.pauli.pauli_mult
andqml.pauli.pauli_mult_with_phase
are now deprecated. Instead, you should useqml.simplify(qml.prod(pauli_1, pauli_2))
to get the reduced operator. (#5057)The private functions
_pauli_mult
,_binary_matrix
and_get_pauli_map
from thepauli
module have been deprecated, as they are no longer used anywhere and the same functionality can be achieved using newer features in thepauli
module. (#5057)Sum.ops
,Sum.coeffs
,Prod.ops
andProd.coeffs
will be deprecated in the future. (#5164)
Documentation ๐
The module documentation for
pennylane.tape
now explains the difference betweenQuantumTape
andQuantumScript
. (#5065)A typo in a code example in the
qml.transforms
API has been fixed. (#5014)Documentation for
qml.data
has been updated and now mentions a way to access the same dataset simultaneously from multiple environments. (#5029)A clarification for the definition of
argnum
added to gradient methods has been made. (#5035)A typo in the code example for
qml.qchem.dipole_of
has been fixed. (#5036)A development guide on deprecations and removals has been added. (#5083)
A note about the eigenspectrum of second-quantized Hamiltonians has been added to
qml.eigvals
. (#5095)A warning about two mathematically equivalent Hamiltonians undergoing different time evolutions has been added to
qml.TrotterProduct
andqml.ApproxTimeEvolution
. (#5137)A reference to the paper that provides the image of the
qml.QAOAEmbedding
template has been added. (#5130)The docstring of
qml.sample
has been updated to advise the use of single-shot expectations instead when differentiating a circuit. (#5237)A quick start page has been added called โImporting Circuitsโ. This explains how to import quantum circuits and operations defined outside of PennyLane. (#5281)
Bug fixes ๐
QubitChannel
can now be used with jitting. (#5288)Fixed a bug in the matplotlib drawer where the colour of
Barrier
did not match the requested style. (#5276)qml.draw
andqml.draw_mpl
now apply all applied transforms before drawing. (#5277)ctrl_decomp_zyz
is now differentiable. (#5198)qml.ops.Pow.matrix()
is now differentiable with TensorFlow with integer exponents. (#5178)The
qml.MottonenStatePreparation
template has been updated to include a global phase operation. (#5166)Fixed a queuing bug when using
qml.prod
with a quantum function that queues a single operator. (#5170)The
qml.TrotterProduct
template has been updated to accept scalar products of operators as an input Hamiltonian. (#5073)Fixed a bug where caching together with JIT compilation and broadcasted tapes yielded wrong results
Operator.hash
now depends on the memory location,id
, of a JAX tracer instead of its string representation. (#3917)qml.transforms.undo_swaps
can now work with operators with hyperparameters or nesting. (#5081)qml.transforms.split_non_commuting
will now pass the original shots along. (#5081)If
argnum
is provided to a gradient transform, only the parameters specified inargnum
will have their gradient methods validated. (#5035)StatePrep
operations expanded onto more wires are now compatible with backprop. (#5028)qml.equal
works well withqml.Sum
operators when wire labels are a mix of integers and strings. (#5037)The return value of
Controlled.generator
now contains a projector that projects onto the correct subspace based on the control value specified. (#5068)CosineWindow
no longer raises an unexpected error when used on a subset of wires at the beginning of a circuit. (#5080)tf.function
now works withTensorSpec(shape=None)
by skipping batch size computation. (#5089)PauliSentence.wires
no longer imposes a false order. (#5041)qml.qchem.import_state
now applies the chemist-to-physicist sign convention when initializing a PennyLane state vector from classically pre-computed wavefunctions. That is, it interleaves spin-up/spin-down operators for the same spatial orbital index, as standard in PennyLane (instead of commuting all spin-up operators to the left, as is standard in quantum chemistry). (#5114)Multi-wire controlled
CNOT
andPhaseShift
are now be decomposed correctly. (#5125) (#5148)draw_mpl
no longer raises an error when drawing a circuit containing an adjoint of a controlled operation. (#5149)default.mixed
no longer throwsValueError
when applying a state vector that is not of typecomplex128
when used with tensorflow. (#5155)ctrl_decomp_zyz
no longer raises aTypeError
if the rotation parameters are of typetorch.Tensor
(#5183)Comparing
Prod
andSum
objects now works regardless of nested structure withqml.equal
if the operators have a validpauli_rep
property. (#5177)Controlled
GlobalPhase
with non-zero control wires no longer throws an error. (#5194)A
QNode
transformed withmitigate_with_zne
now accepts batch parameters. (#5195)The matrix of an empty
PauliSentence
instance is now correct (all-zeros). Further, matrices of emptyPauliWord
andPauliSentence
instances can now be turned into matrices. (#5188)PauliSentence
instances can handle matrix multiplication withPauliWord
instances. (#5208)CompositeOp.eigendecomposition
is now JIT-compatible. (#5207)QubitDensityMatrix
now works with JAX-JIT on thedefault.mixed
device. (#5203) (#5236)When a QNode specifies
diff_method="adjoint"
,default.qubit
no longer tries to decompose non-trainable operations with non-scalar parameters such asQubitUnitary
. (#5233)The overwriting of the class names of
I
,X
,Y
, andZ
no longer happens in the initialization after causing problems with datasets. This now happens globally. (#5252)The
adjoint_metric_tensor
transform now works withjax
. (#5271)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Abhishek Abhishek, Mikhail Andrenkov, Utkarsh Azad, Trenten Babcock, Gabriel Bottrill, Thomas Bromley, Astral Cai, Skylar Chan, Isaac De Vlugt, Diksha Dhawan, Lillian Frederiksen, Pietropaolo Frisoni, Eugenio Gigante, Diego Guala, David Ittah, Soran Jahangiri, Jacky Jiang, Korbinian Kottmann, Christina Lee, Xiaoran Li, Vincent Michaud-Rioux, Romain Moyard, Pablo Antonio Moreno Casares, Erick Ochoa Lopez, Lee J. OโRiordan, Mudit Pandey, Alex Preciado, Matthew Silverman, Jay Soni.
- orphan
Release 0.34.0ยถ
New features since last release
Statistics and drawing for mid-circuit measurements ๐จ
It is now possible to return statistics of composite mid-circuit measurements. (#4888)
Mid-circuit measurement results can be composed using basic arithmetic operations and then statistics can be calculated by putting the result within a PennyLane measurement like
qml.expval()
. For example:import pennylane as qml dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(phi, theta): qml.RX(phi, wires=0) m0 = qml.measure(wires=0) qml.RY(theta, wires=1) m1 = qml.measure(wires=1) return qml.expval(~m0 + m1) print(circuit(1.23, 4.56))
1.2430187928114291
Another option, for ease-of-use when using
qml.sample()
,qml.probs()
, orqml.counts()
, is to provide a simple list of mid-circuit measurement results:dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(phi, theta): qml.RX(phi, wires=0) m0 = qml.measure(wires=0) qml.RY(theta, wires=1) m1 = qml.measure(wires=1) return qml.sample(op=[m0, m1]) print(circuit(1.23, 4.56, shots=5))
[[0 1] [0 1] [0 0] [1 0] [0 1]]
Composite mid-circuit measurement statistics are supported on
default.qubit
anddefault.mixed
. To learn more about which measurements and arithmetic operators are supported, refer to the measurements page and the documentation for qml.measure.Mid-circuit measurements can now be visualized with the text-based
qml.draw()
and the graphicalqml.draw_mpl()
methods. (#4775) (#4803) (#4832) (#4901) (#4850) (#4917) (#4930) (#4957)Drawing of mid-circuit measurement capabilities including qubit reuse and reset, postselection, conditioning, and collecting statistics is now supported. Here is an all-encompassing example:
def circuit(): m0 = qml.measure(0, reset=True) m1 = qml.measure(1, postselect=1) qml.cond(m0 - m1 == 0, qml.S)(0) m2 = qml.measure(1) qml.cond(m0 + m1 == 2, qml.T)(0) qml.cond(m2, qml.PauliX)(1)
The text-based drawer outputs:
>>> print(qml.draw(circuit)()) 0: โโโคโโ โ0โฉโโโโโโโโSโโโโโโโTโโโโโค 1: โโโโโโโโโโโโโคโโโโโโโโโคโโโโโโโXโโค โโโโโโโโโโโโโโโโฌโโโโโโโโฃ โ โโโโโโฉโโโโโโโโ โ โโโโโโโโ
The graphical drawer outputs:
>>> print(qml.draw_mpl(circuit)())
Catalyst is seamlessly integrated with PennyLane โ๏ธ
Catalyst, our next-generation compilation framework, is now accessible within PennyLane, allowing you to more easily benefit from hybrid just-in-time (JIT) compilation.
To access these features, simply install
pennylane-catalyst
:pip install pennylane-catalyst
The qml.compiler module provides support for hybrid quantum-classical compilation. (#4692) (#4979)
Through the use of the
qml.qjit
decorator, entire workflows can be JIT compiled โ including both quantum and classical processing โ down to a machine binary on first-function execution. Subsequent calls to the compiled function will execute the previously-compiled binary, resulting in significant performance improvements.import pennylane as qml dev = qml.device("lightning.qubit", wires=2) @qml.qjit @qml.qnode(dev) def circuit(theta): qml.Hadamard(wires=0) qml.RX(theta, wires=1) qml.CNOT(wires=[0,1]) return qml.expval(qml.PauliZ(wires=1))
>>> circuit(0.5) # the first call, compilation occurs here array(0.) >>> circuit(0.5) # the precompiled quantum function is called array(0.)
Currently, PennyLane supports the Catalyst hybrid compiler with the
qml.qjit
decorator. A significant benefit of Catalyst is the ability to preserve complex control flow around quantum operations โ such asif
statements andfor
loops, and including measurement feedback โ during compilation, while continuing to support end-to-end autodifferentiation.The following functions can now be used with the
qml.qjit
decorator:qml.grad
,qml.jacobian
,qml.vjp
,qml.jvp
, andqml.adjoint
. (#4709) (#4724) (#4725) (#4726)When
qml.grad
orqml.jacobian
are used with@qml.qjit
, they are patched to catalyst.grad and catalyst.jacobian, respectively.dev = qml.device("lightning.qubit", wires=1) @qml.qjit def workflow(x): @qml.qnode(dev) def circuit(x): qml.RX(np.pi * x[0], wires=0) qml.RY(x[1], wires=0) return qml.probs() g = qml.jacobian(circuit) return g(x)
>>> workflow(np.array([2.0, 1.0])) array([[ 3.48786850e-16, -4.20735492e-01], [-8.71967125e-17, 4.20735492e-01]])
JIT-compatible functionality for control flow has been added via
qml.for_loop
,qml.while_loop
, andqml.cond
. (#4698) (#5006)qml.for_loop
andqml.while_loop
can be deployed as decorators on functions that are the body of the loop. The arguments to both follow typical conventions:@qml.for_loop(lower_bound, upper_bound, step)
@qml.while_loop(cond_function)
Here is a concrete example with
qml.for_loop
:qml.for_loop
andqml.while_loop
can be deployed as decorators on functions that are the body of the loop. The arguments to both follow typical conventions:@qml.for_loop(lower_bound, upper_bound, step)
@qml.while_loop(cond_function)
Here is a concrete example with
qml.for_loop
:dev = qml.device("lightning.qubit", wires=1) @qml.qjit @qml.qnode(dev) def circuit(n: int, x: float): @qml.for_loop(0, n, 1) def loop_rx(i, x): # perform some work and update (some of) the arguments qml.RX(x, wires=0) # update the value of x for the next iteration return jnp.sin(x) # apply the for loop final_x = loop_rx(x) return qml.expval(qml.PauliZ(0)), final_x
>>> circuit(7, 1.6) (array(0.97926626), array(0.55395718))
Decompose circuits into the Clifford+T gateset ๐งฉ
The new
qml.clifford_t_decomposition()
transform provides an approximate breakdown of an input circuit into the Clifford+T gateset. Behind the scenes, this decomposition is enacted via thesk_decomposition()
function using the Solovay-Kitaev algorithm. (#4801) (#4802)The Solovay-Kitaev algorithm approximately decomposes a quantum circuit into the Clifford+T gateset. To account for this, a desired total circuit decomposition error,
epsilon
, must be specified when usingqml.clifford_t_decomposition
:dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(): qml.RX(1.1, 0) return qml.state() circuit = qml.clifford_t_decomposition(circuit, epsilon=0.1)
>>> print(qml.draw(circuit)()) 0: โโTโ โโHโโTโ โโHโโTโโHโโTโโHโโTโโHโโTโโHโโTโ โโHโโTโ โโTโ โโHโโTโ โโHโโTโโHโโTโโHโโTโโHโโTโโHโโTโ โโH โโโTโ โโHโโTโโHโโGlobalPhase(0.39)โโค
The resource requirements of this circuit can also be evaluated:
>>> with qml.Tracker(dev) as tracker: ... circuit() >>> resources_lst = tracker.history["resources"] >>> resources_lst[0] wires: 1 gates: 34 depth: 34 shots: Shots(total=None) gate_types: {'Adjoint(T)': 8, 'Hadamard': 16, 'T': 9, 'GlobalPhase': 1} gate_sizes: {1: 33, 0: 1}
Use an iterative approach for quantum phase estimation ๐
Iterative Quantum Phase Estimation is now available with
qml.iterative_qpe
. (#4804)The subroutine can be used similarly to mid-circuit measurements:
import pennylane as qml dev = qml.device("default.qubit", shots=5) @qml.qnode(dev) def circuit(): # Initial state qml.PauliX(wires=[0]) # Iterative QPE measurements = qml.iterative_qpe(qml.RZ(2., wires=[0]), ancilla=[1], iters=3) return [qml.sample(op=meas) for meas in measurements]
>>> print(circuit()) [array([0, 0, 0, 0, 0]), array([1, 0, 0, 0, 0]), array([0, 1, 1, 1, 1])]
The \(i\)-th element in the list refers to the 5 samples generated by the \(i\)-th measurement of the algorithm.
Improvements ๐
Community contributions ๐ฅณ
The
+=
operand can now be used with aPauliSentence
, which has also provides a performance boost. (#4662)The Approximate Quantum Fourier Transform (AQFT) is now available with
qml.AQFT
. (#4715)qml.draw
andqml.draw_mpl
now render operator IDs. (#4749)The ID can be specified as a keyword argument when instantiating an operator:
>>> def circuit(): ... qml.RX(0.123, id="data", wires=0) >>> print(qml.draw(circuit)()) 0: โโRX(0.12,"data")โโค
Non-parametric operators such as
Barrier
,Snapshot
, andWirecut
have been grouped together and moved topennylane/ops/meta.py
. Additionally, the relevant tests have been organized and placed in a new file,tests/ops/test_meta.py
. (#4789)The
TRX
,TRY
, andTRZ
operators are now differentiable via backpropagation ondefault.qutrit
. (#4790)The function
qml.equal
now supportsControlledSequence
operators. (#4829)XZX decomposition has been added to the list of supported single-qubit unitary decompositions. (#4862)
==
and!=
operands can now be used withTransformProgram
andTransformContainers
instances. (#4858)A
qutrit_mixed
module has been added toqml.devices
to store helper functions for a future qutrit mixed-state device. A function calledcreate_initial_state
has been added to this module that creates device-compatible initial states. (#4861)The function
qml.Snapshot
now supports arbitrary state-based measurements (i.e., measurements of typeStateMeasurement
). (#4876)qml.equal
now supports the comparison ofQuantumScript
andBasisRotation
objects. (#4902) (#4919)The function
qml.draw_mpl
now accept a keyword argumentfig
to specify the output figure window. (#4956)
Better support for batching
qml.AmplitudeEmbedding
now supports batching when used with Tensorflow. (#4818)default.qubit
can now evolve already batched states withqml.pulse.ParametrizedEvolution
. (#4863)qml.ArbitraryUnitary
now supports batching. (#4745)Operator and tape batch sizes are evaluated lazily, helping run expensive computations less frequently and an issue with Tensorflow pre-computing batch sizes. (#4911)
Performance improvements and benchmarking
Autograd, PyTorch, and JAX can now use vector-Jacobian products (VJPs) provided by the device from the new device API. If a device provides a VJP, this can be selected by providing
device_vjp=True
to a QNode orqml.execute
. (#4935) (#4557) (#4654) (#4878) (#4841)>>> dev = qml.device('default.qubit') >>> @qml.qnode(dev, diff_method="adjoint", device_vjp=True) >>> def circuit(x): ... qml.RX(x, wires=0) ... return qml.expval(qml.PauliZ(0)) >>> with dev.tracker: ... g = qml.grad(circuit)(qml.numpy.array(0.1)) >>> dev.tracker.totals {'batches': 1, 'simulations': 1, 'executions': 1, 'vjp_batches': 1, 'vjps': 1} >>> g -0.09983341664682815
qml.expval
with largeHamiltonian
objects is now faster and has a significantly lower memory footprint (and constant with respect to the number ofHamiltonian
terms) when theHamiltonian
is aPauliSentence
. This is due to the introduction of a specializeddot
method in thePauliSentence
class which performsPauliSentence
-state
products. (#4839)default.qubit
no longer uses a dense matrix forMultiControlledX
for more than 8 operation wires. (#4673)Some relevant Pytests have been updated to enable its use as a suite of benchmarks. (#4703)
default.qubit
now appliesGroverOperator
faster by not using its matrix representation but a custom rule forapply_operation
. Also, the matrix representation ofGroverOperator
now runs faster. (#4666)A new pipeline to run benchmarks and plot graphs comparing with a fixed reference has been added. This pipeline will run on a schedule and can be activated on a PR with the label
ci:run_benchmarks
. (#4741)default.qubit
now supports adjoint differentiation for arbitrary diagonal state-based measurements. (#4865)The benchmarks pipeline has been expanded to export all benchmark data to a single JSON file and a CSV file with runtimes. This includes all references and local benchmarks. (#4873)
Final phase of updates to transforms
qml.quantum_monte_carlo
andqml.simplify
now use the new transform system. (#4708) (#4949)The formal requirement that type hinting be provided when using the
qml.transform
decorator has been removed. Type hinting can still be used, but is now optional. Please use a type checker such as mypy if you wish to ensure types are being passed correctly. (#4942)
Other improvements
Add PyTree-serialization interface for the
Wires
class. (#4998)PennyLane now supports Python 3.12. (#4985)
SampleMeasurement
now has an optional methodprocess_counts
for computing the measurement results from a counts dictionary. (#4941)A new function called
ops.functions.assert_valid
has been added for checking if anOperator
class is defined correctly. (#4764)Shots
objects can now be multiplied by scalar values. (#4913)GlobalPhase
now decomposes to nothing in case devices do not support global phases. (#4855)Custom operations can now provide their matrix directly through the
Operator.matrix()
method without needing to update thehas_matrix
property.has_matrix
will now automatically beTrue
ifOperator.matrix
is overridden, even ifOperator.compute_matrix
is not. (#4844)The logic for re-arranging states before returning them has been improved. (#4817)
When multiplying
SparseHamiltonian
s by a scalar value, the result now stays as aSparseHamiltonian
. (#4828)trainable_params
can now be set upon initialization of aQuantumScript
instead of having to set the parameter after initialization. (#4877)default.qubit
now calculates the expectation value ofHermitian
operators in a differentiable manner. (#4866)The
rot
decomposition now has support for returning a global phase. (#4869)The
"pennylane_sketch"
MPL-drawer style has been added. This is the same as the"pennylane"
style, but with sketch-style lines. (#4880)Operators now define a
pauli_rep
property, an instance ofPauliSentence
, defaulting toNone
if the operator has not defined it (or has no definition in the Pauli basis). (#4915)qml.ShotAdaptiveOptimizer
can now use a multinomial distribution for spreading shots across the terms of a Hamiltonian measured in a QNode. Note that this is equivalent to what can be done withqml.ExpvalCost
, but this is the preferred method becauseExpvalCost
is deprecated. (#4896)Decomposition of
qml.PhaseShift
now usesqml.GlobalPhase
for retaining the global phase information. (#4657) (#4947)qml.equal
forControlled
operators no longer returnsFalse
when equivalent but differently-ordered sets of control wires and control values are compared. (#4944)All PennyLane
Operator
subclasses are automatically tested byops.functions.assert_valid
to ensure that they follow PennyLaneOperator
standards. (#4922)Probability measurements can now be calculated from a
counts
dictionary with the addition of aprocess_counts
method in theProbabilityMP
class. (#4952)ClassicalShadow.entropy
now uses the algorithm outlined in 1106.5458 to project the approximate density matrix (with potentially negative eigenvalues) onto the closest valid density matrix. (#4959)The
ControlledSequence.compute_decomposition
default now decomposes thePow
operators, improving compatibility with machine learning interfaces. (#4995)
Breaking changes ๐
The function
qml.transforms.classical_jacobian
has been moved to the gradients module and is now accessible asqml.gradients.classical_jacobian
. (#4900)The transforms submodule
qml.transforms.qcut
is now its own module:qml.qcut
. (#4819)The decomposition of
GroverOperator
now has an additional global phase operation. (#4666)qml.cond
and theConditional
operation have been moved from thetransforms
folder to theops/op_math
folder.qml.transforms.Conditional
will now be available asqml.ops.Conditional
. (#4860)The
prep
keyword argument has been removed fromQuantumScript
andQuantumTape
.StatePrepBase
operations should be placed at the beginning of theops
list instead. (#4756)qml.gradients.pulse_generator
is now namedqml.gradients.pulse_odegen
to adhere to paper naming conventions. (#4769)Specifying
control_values
passed toqml.ctrl
as a string is no longer supported. (#4816)The
rot
decomposition will now normalize its rotation angles to the range[0, 4pi]
for consistency (#4869)QuantumScript.graph
is now built usingtape.measurements
instead oftape.observables
because it depended on the now-deprecatedObservable.return_type
property. (#4762)The
"pennylane"
MPL-drawer style now draws straight lines instead of sketch-style lines. (#4880)The default value for the
term_sampling
argument ofShotAdaptiveOptimizer
is nowNone
instead of"weighted_random_sampling"
. (#4896)
Deprecations ๐
single_tape_transform
,batch_transform
,qfunc_transform
, andop_transform
are deprecated. Use the newqml.transform
function instead. (#4774)Observable.return_type
is deprecated. Instead, you should inspect the type of the surrounding measurement process. (#4762) (#4798)All deprecations now raise a
qml.PennyLaneDeprecationWarning
instead of aUserWarning
. (#4814)QuantumScript.is_sampled
andQuantumScript.all_sampled
are deprecated. Users should now validate these properties manually. (#4773)With an algorithmic improvement to
ClassicalShadow.entropy
, the keywordatol
becomes obsolete and will be removed in v0.35. (#4959)
Documentation ๐
Documentation for unitaries and operationsโ decompositions has been moved from
qml.transforms
toqml.ops.ops_math
. (#4906)Documentation for
qml.metric_tensor
andqml.adjoint_metric_tensor
andqml.transforms.classical_jacobian
is now accessible via the gradients API pageqml.gradients
in the documentation. (#4900)Documentation for
qml.specs
has been moved to theresource
module. (#4904)Documentation for QCut has been moved to its own API page:
qml.qcut
. (#4819)The documentation page for
qml.measurements
now links top-level accessible functions (e.g.,qml.expval
) to their top-level pages rather than their module-level pages (e.g.,qml.measurements.expval
). (#4750)Information for the documentation of
qml.matrix
about wire ordering has been added for usingqml.matrix
on a QNode which uses a device withdevice.wires=None
. (#4874)
Bug fixes ๐
TransformDispatcher
now stops queuing when performing the transform when applying it to a qfunc. Only the output of the transform will be queued. (#4983)qml.map_wires
now works properly withqml.cond
andqml.measure
. (#4884)Pow
operators are now picklable. (#4966)Finite differences and SPSA can now be used with tensorflow-autograph on setups that were seeing a bus error. (#4961)
qml.cond
no longer incorrectly queues operators used arguments. (#4948)Attribute
objects now returnFalse
instead of raising aTypeError
when checking if an object is inside the set. (#4933)Fixed a bug where the parameter-shift rule of
qml.ctrl(op)
was wrong ifop
had a generator that has two or more eigenvalues and is stored as aSparseHamiltonian
. (#4899)Fixed a bug where trainable parameters in the post-processing of finite-differences were incorrect for JAX when applying the transform directly on a QNode. (#4879)
qml.grad
andqml.jacobian
now explicitly raise errors if trainable parameters are integers. (#4836)JAX-JIT now works with shot vectors. (#4772)
JAX can now differentiate a batch of circuits where one tape does not have trainable parameters. (#4837)
The decomposition of
GroverOperator
now has the same global phase as its matrix. (#4666)The
tape.to_openqasm
method no longer mistakenly includes interface information in the parameter string when converting tapes using non-NumPy interfaces. (#4849)qml.defer_measurements
now correctly transforms circuits when terminal measurements include wires used in mid-circuit measurements. (#4787)Fixed a bug where the adjoint differentiation method would fail if an operation that has a parameter with
grad_method=None
is present. (#4820)MottonenStatePreparation
andBasisStatePreparation
now raise an error when decomposing a broadcasted state vector. (#4767)Gradient transforms now work with overridden shot vectors and
default.qubit
. (#4795)Any
ScalarSymbolicOp
, likeEvolution
, now states that it has a matrix if the target is aHamiltonian
. (#4768)In
default.qubit
, initial states are now initialized with the simulatorโs wire order, not the circuitโs wire order. (#4781)qml.compile
will now always decompose toexpand_depth
, even if a target basis set is not specified. (#4800)qml.transforms.transpile
can now handle measurements that are broadcasted onto all wires. (#4793)Parametrized circuits whose operators do not act on all wires return PennyLane tensors instead of NumPy arrays, as expected. (#4811) (#4817)
qml.transforms.merge_amplitude_embedding
no longer depends on queuing, allowing it to work as expected with QNodes. (#4831)qml.pow(op)
andqml.QubitUnitary.pow()
now also work with Tensorflow data raised to an integer power. (#4827)The text drawer has been fixed to correctly label
qml.qinfo
measurements, as well asqml.classical_shadow
qml.shadow_expval
. (#4803)Removed an implicit assumption that an empty
PauliSentence
gets treated as identity under multiplication. (#4887)Using a
CNOT
orPauliZ
operation with large batched states and the Tensorflow interface no longer raises an unexpected error. (#4889)qml.map_wires
no longer fails when mapping nested quantum tapes. (#4901)Conversion of circuits to openqasm now decomposes to a depth of 10, allowing support for operators requiring more than 2 iterations of decomposition, such as the
ApproxTimeEvolution
gate. (#4951)MPLDrawer
does not add the bonus space for classical wires when no classical wires are present. (#4987)Projector
now works with parameter-broadcasting. (#4993)The jax-jit interface can now be used with float32 mode. (#4990)
Keras models with a
qnn.KerasLayer
no longer fail to save and load weights properly when they are named โweightsโ. (#5008)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Guillermo Alonso, Ali Asadi, Utkarsh Azad, Gabriel Bottrill, Thomas Bromley, Astral Cai, Minh Chau, Isaac De Vlugt, Amintor Dusko, Pieter Eendebak, Lillian Frederiksen, Pietropaolo Frisoni, Josh Izaac, Juan Giraldo, Emiliano Godinez Ramirez, Ankit Khandelwal, Korbinian Kottmann, Christina Lee, Vincent Michaud-Rioux, Anurav Modak, Romain Moyard, Mudit Pandey, Matthew Silverman, Jay Soni, David Wierichs, Justin Woodring, Sergei Mironov.
- orphan
Release 0.33.1ยถ
Bug fixes ๐
Fix gradient performance regression due to expansion of VJP products. (#4806)
qml.defer_measurements
now correctly transforms circuits when terminal measurements include wires used in mid-circuit measurements. (#4787)Any
ScalarSymbolicOp
, likeEvolution
, now states that it has a matrix if the target is aHamiltonian
. (#4768)In
default.qubit
, initial states are now initialized with the simulatorโs wire order, not the circuitโs wire order. (#4781)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Christina Lee, Lee James OโRiordan, Mudit Pandey
- orphan
Release 0.33.0ยถ
New features since last release
Postselection and statistics in mid-circuit measurements ๐
It is now possible to request postselection on a mid-circuit measurement. (#4604)
This can be achieved by specifying the
postselect
keyword argument inqml.measure
as either0
or1
, corresponding to the basis states.import pennylane as qml dev = qml.device("default.qubit") @qml.qnode(dev, interface=None) def circuit(): qml.Hadamard(wires=0) qml.CNOT(wires=[0, 1]) qml.measure(0, postselect=1) return qml.expval(qml.PauliZ(1)), qml.sample(wires=1)
This circuit prepares the \(| \Phi^{+} \rangle\) Bell state and postselects on measuring \(|1\rangle\) in wire
0
. The output of wire1
is then also \(|1\rangle\) at all times:>>> circuit(shots=10) (-1.0, array([1, 1, 1, 1, 1, 1]))
Note that the number of shots is less than the requested amount because we have thrown away the samples where \(|0\rangle\) was measured in wire
0
.Measurement statistics can now be collected for mid-circuit measurements. (#4544)
dev = qml.device("default.qubit") @qml.qnode(dev) def circ(x, y): qml.RX(x, wires=0) qml.RY(y, wires=1) m0 = qml.measure(1) return qml.expval(qml.PauliZ(0)), qml.expval(m0), qml.sample(m0)
>>> circ(1.0, 2.0, shots=10000) (0.5606, 0.7089, array([0, 1, 1, ..., 1, 1, 1]))
Support is provided for both finite-shot and analytic modes and devices default to using the deferred measurement principle to enact the mid-circuit measurements.
Exponentiate Hamiltonians with flexible Trotter products ๐
Higher-order Trotter-Suzuki methods are now easily accessible through a new operation called
TrotterProduct
. (#4661)Trotterization techniques are an affective route towards accurate and efficient Hamiltonian simulation. The Suzuki-Trotter product formula allows for the ability to express higher-order approximations to the matrix exponential of a Hamiltonian, and it is now available to use in PennyLane via the
TrotterProduct
operation. Simply specify theorder
of the approximation and the evolutiontime
.coeffs = [0.25, 0.75] ops = [qml.PauliX(0), qml.PauliZ(0)] H = qml.dot(coeffs, ops) dev = qml.device("default.qubit", wires=2) @qml.qnode(dev) def circuit(): qml.Hadamard(0) qml.TrotterProduct(H, time=2.4, order=2) return qml.state()
>>> circuit() [-0.13259524+0.59790098j 0. +0.j -0.13259524-0.77932754j 0. +0.j ]
Approximating matrix exponentiation with random product formulas, qDrift, is now available with the new
QDrift
operation. (#4671)As shown in 1811.08017, qDrift is a Markovian process that can provide a speedup in Hamiltonian simulation. At a high level, qDrift works by randomly sampling from the Hamiltonian terms with a probability that depends on the Hamiltonian coefficients. This method for Hamiltonian simulation is now ready to use in PennyLane with the
QDrift
operator. Simply specify the evolutiontime
and the number of samples drawn from the Hamiltonian,n
:coeffs = [0.25, 0.75] ops = [qml.PauliX(0), qml.PauliZ(0)] H = qml.dot(coeffs, ops) dev = qml.device("default.qubit", wires=2) @qml.qnode(dev) def circuit(): qml.Hadamard(0) qml.QDrift(H, time=1.2, n = 10) return qml.probs()
>>> circuit() array([0.61814334, 0. , 0.38185666, 0. ])
Building blocks for quantum phase estimation ๐งฑ
A new operator called
CosineWindow
has been added to prepare an initial state based on a cosine wave function. (#4683)As outlined in 2110.09590, the cosine tapering window is part of a modification to quantum phase estimation that can provide a cubic improvement to the algorithmโs error rate. Using
CosineWindow
will prepare a state whose amplitudes follow a cosinusoidal distribution over the computational basis.import matplotlib.pyplot as plt dev = qml.device('default.qubit', wires=4) @qml.qnode(dev) def example_circuit(): qml.CosineWindow(wires=range(4)) return qml.state() output = example_circuit() plt.style.use("pennylane.drawer.plot") plt.bar(range(len(output)), output) plt.show()
Controlled gate sequences raised to decreasing powers, a sub-block in quantum phase estimation, can now be created with the new
ControlledSequence
operator. (#4707)To use
ControlledSequence
, specify the controlled unitary operator and the control wires,control
:dev = qml.device("default.qubit", wires = 4) @qml.qnode(dev) def circuit(): for i in range(3): qml.Hadamard(wires = i) qml.ControlledSequence(qml.RX(0.25, wires = 3), control = [0, 1, 2]) qml.adjoint(qml.QFT)(wires = range(3)) return qml.probs(wires = range(3))
>>> print(circuit()) [0.92059345 0.02637178 0.00729619 0.00423258 0.00360545 0.00423258 0.00729619 0.02637178]
New device capabilities, integration with Catalyst, and more! โ๏ธ
default.qubit
now uses the newqml.devices.Device
API and functionality inqml.devices.qubit
. If you experience any issues with the updateddefault.qubit
, please let us know by posting an issue. The old version of the device is still accessible by the short namedefault.qubit.legacy
, or directly viaqml.devices.DefaultQubitLegacy
. (#4594) (#4436) (#4620) (#4632)This changeover has a number of benefits for
default.qubit
, including:The number of wires is now optional โ simply having
qml.device("default.qubit")
is valid! If wires are not provided at instantiation, the device automatically infers the required number of wires for each circuit provided for execution.dev = qml.device("default.qubit") @qml.qnode(dev) def circuit(): qml.PauliZ(0) qml.RZ(0.1, wires=1) qml.Hadamard(2) return qml.state()
>>> print(qml.draw(circuit)()) 0: โโZโโโโโโโโโค State 1: โโRZ(0.10)โโค State 2: โโHโโโโโโโโโค State
default.qubit
is no longer silently swapped out with an interface-appropriate device when the backpropagation differentiation method is used. For example, consider:import jax dev = qml.device("default.qubit", wires=1) @qml.qnode(dev, diff_method="backprop") def f(x): qml.RX(x, wires=0) return qml.expval(qml.PauliZ(0)) f(jax.numpy.array(0.2))
In previous versions of PennyLane, the device will be swapped for the JAX equivalent:
>>> f.device <DefaultQubitJax device (wires=1, shots=None) at 0x7f8c8bff50a0> >>> f.device == dev False
Now,
default.qubit
can itself dispatch to all the interfaces in a backprop-compatible way and hence does not need to be swapped:>>> f.device <default.qubit device (wires=1) at 0x7f20d043b040> >>> f.device == dev True
A QNode that has been decorated with
qjit
from PennyLaneโs Catalyst library for just-in-time hybrid compilation is now compatible withqml.draw
. (#4609)import catalyst @catalyst.qjit @qml.qnode(qml.device("lightning.qubit", wires=3)) def circuit(x, y, z, c): """A quantum circuit on three wires.""" @catalyst.for_loop(0, c, 1) def loop(i): qml.Hadamard(wires=i) qml.RX(x, wires=0) loop() qml.RY(y, wires=1) qml.RZ(z, wires=2) return qml.expval(qml.PauliZ(0)) draw = qml.draw(circuit, decimals=None)(1.234, 2.345, 3.456, 1)
>>> print(draw) 0: โโRXโโHโโโค <Z> 1: โโHโโโRYโโค 2: โโRZโโโโโโค
Improvements ๐
More PyTrees!
MeasurementProcess
andQuantumScript
objects are now registered as JAX PyTrees. (#4607) (#4608)It is now possible to JIT-compile functions with arguments that are a
MeasurementProcess
or aQuantumScript
:import jax tape0 = qml.tape.QuantumTape([qml.RX(1.0, 0), qml.RY(0.5, 0)], [qml.expval(qml.PauliZ(0))]) dev = qml.device('lightning.qubit', wires=5) execute_kwargs = {"device": dev, "gradient_fn": qml.gradients.param_shift, "interface":"jax"} jitted_execute = jax.jit(qml.execute, static_argnames=execute_kwargs.keys()) jitted_execute((tape0, ), **execute_kwargs)
Improving QChem and existing algorithms
Computationally expensive functions in
integrals.py
,electron_repulsion
and_hermite_coulomb
, have been modified to replace indexing with slicing for better compatibility with JAX. (#4685)qml.qchem.import_state
has been extended to import more quantum chemistry wavefunctions, from MPS, DMRG and SHCI classical calculations performed with the Block2 and Dice libraries. #4523 #4524 #4626 #4634Check out our how-to guide to learn more about how PennyLane integrates with your favourite quantum chemistry libraries.
The qchem
fermionic_dipole
andparticle_number
functions have been updated to use aFermiSentence
. The deprecated features for using tuples to represent fermionic operations are removed. (#4546) (#4556)The tensor-network template
qml.MPS
now supports changing theoffset
between subsequent blocks for more flexibility. (#4531)Builtin types support with
qml.pauli_decompose
have been improved. (#4577)AmplitudeEmbedding
now inherits fromStatePrep
, allowing for it to not be decomposed when at the beginning of a circuit, thus behaving likeStatePrep
. (#4583)qml.cut_circuit
is now compatible with circuits that compute the expectation values of Hamiltonians with two or more terms. (#4642)
Next-generation device API
default.qubit
now tracks the number of equivalent qpu executions and total shots when the device is sampling. Note that"simulations"
denotes the number of simulation passes, whereas"executions"
denotes how many different computational bases need to be sampled in. Additionally, the newdefault.qubit
tracks the results ofdevice.execute
. (#4628) (#4649)DefaultQubit
can now accept ajax.random.PRNGKey
as aseed
to set the key for the JAX pseudo random number generator when using the JAX interface. This corresponds to theprng_key
ondefault.qubit.jax
in the old API. (#4596)The
JacobianProductCalculator
abstract base class and implementationsTransformJacobianProducts
DeviceDerivatives
, andDeviceJacobianProducts
have been added topennylane.interfaces.jacobian_products
. (#4435) (#4527) (#4637)DefaultQubit
dispatches to a faster implementation for applyingParametrizedEvolution
to a state when it is more efficient to evolve the state than the operation matrix. (#4598) (#4620)Wires can be provided to the new device API. (#4538) (#4562)
qml.sample()
in the new device API now returns anp.int64
array instead ofnp.bool8
. (#4539)The new device API now has a
repr()
method. (#4562)DefaultQubit
now works as expected with measurement processes that donโt specify wires. (#4580)Various improvements to measurements have been made for feature parity between
default.qubit.legacy
and the newDefaultQubit
. This includes not trying to squeeze batchedCountsMP
results and implementingMutualInfoMP.map_wires
. (#4574)devices.qubit.simulate
now accepts an interface keyword argument. If a QNode withDefaultQubit
specifies an interface, the result will be computed with that interface. (#4582)ShotAdaptiveOptimizer
has been updated to pass shots to QNode executions instead of overriding device shots before execution. This makes it compatible with the new device API. (#4599)pennylane.devices.preprocess
now offers the transformsdecompose
,validate_observables
,validate_measurements
,validate_device_wires
,validate_multiprocessing_workers
,warn_about_trainable_observables
, andno_sampling
to assist in constructing devices under the new device API. (#4659)Updated
qml.device
,devices.preprocessing
and thetape_expand.set_decomposition
context manager to bringDefaultQubit
to feature parity withdefault.qubit.legacy
with regards to using custom decompositions. TheDefaultQubit
device can now be included in aset_decomposition
context or initialized with acustom_decomps
dictionary, as well as a custommax_depth
for decomposition. (#4675)
Other improvements
The
StateMP
measurement now accepts a wire order (e.g., a device wire order). Theprocess_state
method will re-order the given state to go from the inputted wire-order to the processโs wire-order. If the processโs wire-order contains extra wires, it will assume those are in the zero-state. (#4570) (#4602)Methods called
add_transform
andinsert_front_transform
have been added toTransformProgram
. (#4559)Instances of the
TransformProgram
class can now be added together. (#4549)Transforms can now be applied to devices following the new device API. (#4667)
All gradient transforms have been updated to the new transform program system. (#4595)
Multi-controlled operations with a single-qubit special unitary target can now automatically decompose. (#4697)
pennylane.defer_measurements
will now exit early if the input does not contain mid circuit measurements. (#4659)The density matrix aspects of
StateMP
have been split into their own measurement process calledDensityMatrixMP
. (#4558)StateMeasurement.process_state
now assumes that the input is flat.ProbabilityMP.process_state
has been updated to reflect this assumption and avoid redundant reshaping. (#4602)qml.exp
returns a more informative error message when decomposition is unavailable for non-unitary operators. (#4571)Added
qml.math.get_deep_interface
to get the interface of a scalar hidden deep in lists or tuples. (#4603)Updated
qml.math.ndim
andqml.math.shape
to work with built-in lists or tuples that contain interface-specific scalar dat (e.g.,[(tf.Variable(1.1), tf.Variable(2.2))]
). (#4603)When decomposing a unitary matrix with
one_qubit_decomposition
and opting to include theGlobalPhase
in the decomposition, the phase is no longer cast todtype=complex
. (#4653)_qfunc_output
has been removed fromQuantumScript
, as it is no longer necessary. There is still a_qfunc_output
property onQNode
instances. (#4651)qml.data.load
properly handles parameters that come after'full'
(#4663)The
qml.jordan_wigner
function has been modified to optionally remove the imaginary components of the computed qubit operator, if imaginary components are smaller than a threshold. (#4639)qml.data.load
correctly performs a full download of the dataset after a partial download of the same dataset has already been performed. (#4681)The performance of
qml.data.load()
has been improved when partially loading a dataset (#4674)Plots generated with the
pennylane.drawer.plot
style ofmatplotlib.pyplot
now have black axis labels and are generated at a default DPI of 300. (#4690)Shallow copies of the
QNode
now also copy theexecute_kwargs
and transform program. When applying a transform to aQNode
, the new qnode is only a shallow copy of the original and thus keeps the same device. (#4736)QubitDevice
andCountsMP
are updated to disregard samples containing failed hardware measurements (record asnp.NaN
) when tallying samples, rather than counting failed measurements as ground-state measurements, and to displayqml.counts
coming from these hardware devices correctly. (#4739)
Breaking changes ๐
qml.defer_measurements
now raises an error if a transformed circuit measuresqml.probs
,qml.sample
, orqml.counts
without any wires or observable, or if it measuresqml.state
. (#4701)The device test suite now converts device keyword arguments to integers or floats if possible. (#4640)
MeasurementProcess.eigvals()
now raises anEigvalsUndefinedError
if the measurement observable does not have eigenvalues. (#4544)The
__eq__
and__hash__
methods ofOperator
andMeasurementProcess
no longer rely on the objectโs address in memory. Using==
with operators and measurement processes will now behave the same asqml.equal
, and objects of the same type with the same data and hyperparameters will have the same hash. (#4536)In the following scenario, the second and third code blocks show the previous and current behaviour of operator and measurement process equality, determined by
==
:op1 = qml.PauliX(0) op2 = qml.PauliX(0) op3 = op1
Old behaviour:
>>> op1 == op2 False >>> op1 == op3 True
New behaviour:
>>> op1 == op2 True >>> op1 == op3 True
The
__hash__
dunder method defines the hash of an object. The default hash of an object is determined by the objects memory address. However, the new hash is determined by the properties and attributes of operators and measurement processes. Consider the scenario below. The second and third code blocks show the previous and current behaviour.op1 = qml.PauliX(0) op2 = qml.PauliX(0)
Old behaviour:
>>> print({op1, op2}) {PauliX(wires=[0]), PauliX(wires=[0])}
New behaviour:
>>> print({op1, op2}) {PauliX(wires=[0])}
The old return type and associated functions
qml.enable_return
andqml.disable_return
have been removed. (#4503)The
mode
keyword argument inQNode
has been removed. Please usegrad_on_execution
instead. (#4503)The CV observables
qml.X
andqml.P
have been removed. Please useqml.QuadX
andqml.QuadP
instead. (#4533)The
sampler_seed
argument ofqml.gradients.spsa_grad
has been removed. Instead, thesampler_rng
argument should be set, either to an integer value, which will be used to create a PRNG internally, or to a NumPy pseudo-random number generator (PRNG) created vianp.random.default_rng(seed)
. (#4550)The
QuantumScript.set_parameters
method and theQuantumScript.data
setter have been removed. Please useQuantumScript.bind_new_parameters
instead. (#4548)The method
tape.unwrap()
and correspondingUnwrapTape
andUnwrap
classes have been removed. Instead oftape.unwrap()
, useqml.transforms.convert_to_numpy_parameters
. (#4535)The
RandomLayers.compute_decomposition
keyword argumentratio_imprivitive
has been changed toratio_imprim
to match the call signature of the operation. (#4552)The private
TmpPauliRot
operator used forSpecialUnitary
no longer decomposes to nothing when the theta value is trainable. (#4585)ProbabilityMP.marginal_prob
has been removed. Its contents have been moved intoprocess_state
, which effectively just calledmarginal_prob
withnp.abs(state) ** 2
. (#4602)
Deprecations ๐
The following decorator syntax for transforms has been deprecated and will raise a warning: (#4457)
@transform_fn(**transform_kwargs) @qml.qnode(dev) def circuit(): ...
If you are using a transform that has supporting
transform_kwargs
, please call the transform directly usingcircuit = transform_fn(circuit, **transform_kwargs)
, or usefunctools.partial
:@functools.partial(transform_fn, **transform_kwargs) @qml.qnode(dev) def circuit(): ...
The
prep
keyword argument inQuantumScript
has been deprecated and will be removed fromQuantumScript
.StatePrepBase
operations should be placed at the beginning of theops
list instead. (#4554)qml.gradients.pulse_generator
has been renamed toqml.gradients.pulse_odegen
to adhere to paper naming conventions. During v0.33,pulse_generator
is still available but raises a warning. (#4633)
Documentation ๐
A warning section in the docstring for
DefaultQubit
regarding the start method used in multiprocessing has been added. This may help users circumvent issues arising in Jupyter notebooks on macOS for example. (#4622)Documentation improvements to the new device API have been made. The documentation now correctly states that interface-specific parameters are only passed to the device for backpropagation derivatives. (#4542)
Functions for qubit-simulation to the
qml.devices
sub-page of the โInternalโ section have been added. Note that these functions are unstable while device upgrades are underway. (#4555)A documentation improvement to the usage example in the
qml.QuantumMonteCarlo
page has been made. An integral was missing the differential \(dx\). (#4593)A documentation improvement for the use of the
pennylane
style ofqml.drawer
and thepennylane.drawer.plot
style ofmatplotlib.pyplot
has been made by clarifying the use of the default font. (#4690)
Bug fixes ๐
Jax jit now works when a probability measurement is broadcasted onto all wires. (#4742)
Fixed
LocalHilbertSchmidt.compute_decomposition
so that the template can be used in a QNode. (#4719)Fixes
transforms.transpile
with arbitrary measurement processes. (#4732)Providing
work_wires=None
toqml.GroverOperator
no longer interpretsNone
as a wire. (#4668)Fixed an issue where the
__copy__
method of theqml.Select()
operator attempted to access un-initialized data. (#4551)Fixed the
skip_first
option inexpand_tape_state_prep
. (#4564)convert_to_numpy_parameters
now usesqml.ops.functions.bind_new_parameters
. This reinitializes the operation and makes sure everything references the new NumPy parameters. (#4540)tf.function
no longer breaksProbabilityMP.process_state
, which is needed by new devices. (#4470)Fixed unit tests for
qml.qchem.mol_data
. (#4591)Fixed
ProbabilityMP.process_state
so that it allows for proper Autograph compilation. Without this, decorating a QNode that returns anexpval
withtf.function
would fail when computing the expectation. (#4590)The
torch.nn.Module
properties are now accessible on apennylane.qnn.TorchLayer
. (#4611)qml.math.take
with Pytorch now returnstensor[..., indices]
when the user requests the last axis (axis=-1
). Without the fix, it would wrongly returntensor[indices]
. (#4605)Ensured the logging
TRACE
level works with gradient-free execution. (#4669)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Guillermo Alonso, Utkarsh Azad, Thomas Bromley, Isaac De Vlugt, Jack Brown, Stepan Fomichev, Joana Fraxanet, Diego Guala, Soran Jahangiri, Edward Jiang, Korbinian Kottmann, Ivana Kureฤiฤ Christina Lee, Lillian M. A. Frederiksen, Vincent Michaud-Rioux, Romain Moyard, Daniel F. Nino, Lee James OโRiordan, Mudit Pandey, Matthew Silverman, Jay Soni.
- orphan
Release 0.32.0ยถ
New features since last release
Encode matrices using a linear combination of unitaries โ๏ธ๏ธ
It is now possible to encode an operator
A
into a quantum circuit by decomposing it into a linear combination of unitaries using PREP (qml.StatePrep) and SELECT (qml.Select) routines. (#4431) (#4437) (#4444) (#4450) (#4506) (#4526)Consider an operator
A
composed of a linear combination of Pauli terms:>>> A = qml.PauliX(2) + 2 * qml.PauliY(2) + 3 * qml.PauliZ(2)
A decomposable block-encoding circuit can be created:
def block_encode(A, control_wires): probs = A.coeffs / np.sum(A.coeffs) state = np.pad(np.sqrt(probs, dtype=complex), (0, 1)) unitaries = A.ops qml.StatePrep(state, wires=control_wires) qml.Select(unitaries, control=control_wires) qml.adjoint(qml.StatePrep)(state, wires=control_wires)
>>> print(qml.draw(block_encode, show_matrices=False)(A, control_wires=[0, 1])) 0: โโญ|ฮจโฉโโญSelectโโญ|ฮจโฉโ โโค 1: โโฐ|ฮจโฉโโSelectโโฐ|ฮจโฉโ โโค 2: โโโโโโโฐSelectโโโโโโโโค
This circuit can be used as a building block within a larger QNode to perform algorithms such as QSVT and Hamiltonian simulation.
Decomposing a Hermitian matrix into a linear combination of Pauli words via
qml.pauli_decompose
is now faster and differentiable. (#4395) (#4479) (#4493)def find_coeffs(p): mat = np.array([[3, p], [p, 3]]) A = qml.pauli_decompose(mat) return A.coeffs
>>> import jax >>> from jax import numpy as np >>> jax.jacobian(find_coeffs)(np.array(2.)) Array([0., 1.], dtype=float32, weak_type=True)
Monitor PennyLane's inner workings with logging ๐
Python-native logging can now be enabled with
qml.logging.enable_logging()
. (#4377) (#4383)Consider the following code that is contained in
my_code.py
:import pennylane as qml qml.logging.enable_logging() # enables logging dev = qml.device("default.qubit", wires=2) @qml.qnode(dev) def f(x): qml.RX(x, wires=0) return qml.state() f(0.5)
Executing
my_code.py
with logging enabled will detail every step in PennyLaneโs pipeline that gets used to run your code.$ python my_code.py [1967-02-13 15:18:38,591][DEBUG][<PID 8881:MainProcess>] - pennylane.qnode.__init__()::"Creating QNode(func=<function f at 0x7faf2a6fbaf0>, device=<DefaultQubit device (wires=2, shots=None) at 0x7faf2a689b50>, interface=auto, diff_method=best, expansion_strategy=gradient, max_expansion=10, grad_on_execution=best, mode=None, cache=True, cachesize=10000, max_diff=1, gradient_kwargs={}" ...
Additional logging configuration settings can be specified by modifying the contents of the logging configuration file, which can be located by running
qml.logging.config_path()
. Follow our logging docs page for more details!
More input states for quantum chemistry calculations โ๏ธ
Input states obtained from advanced quantum chemistry calculations can be used in a circuit. (#4427) (#4433) (#4461) (#4476) (#4505)
Quantum chemistry calculations rely on an initial state that is typically selected to be the trivial Hartree-Fock state. For molecules with a complicated electronic structure, using initial states obtained from affordable post-Hartree-Fock calculations helps to improve the efficiency of the quantum simulations. These calculations can be done with external quantum chemistry libraries such as PySCF.
It is now possible to import a PySCF solver object in PennyLane and extract the corresponding wave function in the form of a state vector that can be directly used in a circuit. First, perform your classical quantum chemistry calculations and then use the qml.qchem.import_state function to import the solver object and return a state vector.
>>> from pyscf import gto, scf, ci
>>> mol = gto.M(atom=[['H', (0, 0, 0)], ['H', (0,0,0.71)]], basis='sto6g')
>>> myhf = scf.UHF(mol).run()
>>> myci = ci.UCISD(myhf).run()
>>> wf_cisd = qml.qchem.import_state(myci, tol=1e-1)
>>> print(wf_cisd)
[ 0. +0.j 0. +0.j 0. +0.j 0.1066467 +0.j
1. +0.j 0. +0.j 0. +0.j 0. +0.j
2. +0.j 0. +0.j 0. +0.j 0. +0.j
-0.99429698+0.j 0. +0.j 0. +0.j 0. +0.j]
The state vector can be implemented in a circuit using ``qml.StatePrep``.
>>> dev = qml.device('default.qubit', wires=4)
>>> @qml.qnode(dev)
... def circuit():
... qml.StatePrep(wf_cisd, wires=range(4))
... return qml.state()
>>> print(circuit())
[ 0. +0.j 0. +0.j 0. +0.j 0.1066467 +0.j
1. +0.j 0. +0.j 0. +0.j 0. +0.j
2. +0.j 0. +0.j 0. +0.j 0. +0.j
-0.99429698+0.j 0. +0.j 0. +0.j 0. +0.j]
The currently supported post-Hartree-Fock methods are RCISD, UCISD, RCCSD, and UCCSD which
denote restricted (R) and unrestricted (U) configuration interaction (CI) and coupled cluster (CC)
calculations with single and double (SD) excitations.
Reuse and reset qubits after mid-circuit measurements โป๏ธ
PennyLane now allows you to define circuits that reuse a qubit after a mid-circuit measurement has taken place. Optionally, the wire can also be reset to the \(|0\rangle\) state. (#4402) (#4432)
Post-measurement reset can be activated by setting
reset=True
when calling qml.measure. In this version of PennyLane, executing circuits with qubit reuse will result in the defer_measurements transform being applied. This transform replaces each reused wire with an additional qubit. However, future releases of PennyLane will explore device-level support for qubit reuse without consuming additional qubits.Qubit reuse and reset is also fully differentiable:
dev = qml.device("default.qubit", wires=4) @qml.qnode(dev) def circuit(p): qml.RX(p, wires=0) m = qml.measure(0, reset=True) qml.cond(m, qml.Hadamard)(1) qml.RX(p, wires=0) m = qml.measure(0) qml.cond(m, qml.Hadamard)(1) return qml.expval(qml.PauliZ(1))
>>> jax.grad(circuit)(0.4) Array(-0.35867804, dtype=float32, weak_type=True)
You can read more about mid-circuit measurements in the documentation, and stay tuned for more mid-circuit measurement features in the next few releases!
Improvements ๐
A new PennyLane drawing style
Circuit drawings and plots can now be created following a PennyLane style. (#3950)
The
qml.draw_mpl
function accepts astyle='pennylane'
argument to create PennyLane themed circuit diagrams:def circuit(x, z): qml.QFT(wires=(0,1,2,3)) qml.Toffoli(wires=(0,1,2)) qml.CSWAP(wires=(0,2,3)) qml.RX(x, wires=0) qml.CRZ(z, wires=(3,0)) return qml.expval(qml.PauliZ(0)) qml.draw_mpl(circuit, style="pennylane")(1, 1)
PennyLane-styled plots can also be drawn by passing
"pennylane.drawer.plot"
to Matplotlibโsplt.style.use
function:import matplotlib.pyplot as plt plt.style.use("pennylane.drawer.plot") for i in range(3): plt.plot(np.random.rand(10))
If the font Quicksand Bold isnโt available, an available default font is used instead.
Making operators immutable and PyTrees
Any class inheriting from
Operator
is now automatically registered as a pytree with JAX. This unlocks the ability to jit functions ofOperator
. (#4458)>>> op = qml.adjoint(qml.RX(1.0, wires=0)) >>> jax.jit(qml.matrix)(op) Array([[0.87758255-0.j , 0. +0.47942555j], [0. +0.47942555j, 0.87758255-0.j ]], dtype=complex64, weak_type=True) >>> jax.tree_util.tree_map(lambda x: x+1, op) Adjoint(RX(2.0, wires=[0]))
All
Operator
objects now defineOperator._flatten
andOperator._unflatten
methods that separate trainable from untrainable components. These methods will be used in serialization and pytree registration. Custom operations may need an update to ensure compatibility with new PennyLane features. (#4483) (#4314)The
QuantumScript
class now has abind_new_parameters
method that allows creation of newQuantumScript
objects with the provided parameters. (#4345)The
qml.gradients
module no longer mutates operators in-place for any gradient transforms. Instead, operators that need to be mutated are copied with new parameters. (#4220)PennyLane no longer directly relies on
Operator.__eq__
. (#4398)qml.equal
no longer raises errors when operators or measurements of different types are compared. Instead, it returnsFalse
. (#4315)
Transforms
Transform programs are now integrated with the QNode. (#4404)
def null_postprocessing(results: qml.typing.ResultBatch) -> qml.typing.Result: return results[0] @qml.transforms.core.transform def scale_shots(tape: qml.tape.QuantumTape, shot_scaling) -> (Tuple[qml.tape.QuantumTape], Callable): new_shots = tape.shots.total_shots * shot_scaling new_tape = qml.tape.QuantumScript(tape.operations, tape.measurements, shots=new_shots) return (new_tape, ), null_postprocessing dev = qml.devices.experimental.DefaultQubit2() @partial(scale_shots, shot_scaling=2) @qml.qnode(dev, interface=None) def circuit(): return qml.sample(wires=0)
>>> circuit(shots=1) array([False, False])
Transform Programs,
qml.transforms.core.TransformProgram
, can now be called on a batch of circuits and return a new batch of circuits and a single post processing function. (#4364)TransformDispatcher
now allows registration of custom QNode transforms. (#4466)QNode transforms in
qml.qinfo
now support custom wire labels. #4331qml.transforms.adjoint_metric_tensor
now uses the simulation tools inqml.devices.qubit
instead of private methods ofqml.devices.DefaultQubit
. (#4456)Auxiliary wires and device wires are now treated the same way in
qml.transforms.metric_tensor
as inqml.gradients.hadamard_grad
. All valid wire input formats foraux_wire
are supported. (#4328)
Next-generation device API
The experimental device interface has been integrated with the QNode for JAX, JAX-JIT, TensorFlow and PyTorch. (#4323) (#4352) (#4392) (#4393)
The experimental
DefaultQubit2
device now supports computing VJPs and JVPs using the adjoint method. (#4374)New functions called
adjoint_jvp
andadjoint_vjp
that compute the JVP and VJP of a tape using the adjoint method have been added toqml.devices.qubit.adjoint_jacobian
(#4358)DefaultQubit2
now accepts amax_workers
argument which controls multiprocessing. AProcessPoolExecutor
executes tapes asynchronously using a pool of at mostmax_workers
processes. Ifmax_workers
isNone
or not given, only the current process executes tapes. If you experience any issue, say using JAX, TensorFlow, Torch, try settingmax_workers
toNone
. (#4319) (#4425)qml.devices.experimental.Device
now accepts a shots keyword argument and has ashots
property. This property is only used to set defaults for a workflow, and does not directly influence the number of shots used in executions or derivatives. (#4388)expand_fn()
forDefaultQubit2
has been updated to decomposeStatePrep
operations present in the middle of a circuit. (#4444)If no seed is specified on initialization with
DefaultQubit2
, the local random number generator will be seeded from NumPyโs global random number generator. (#4394)
Improvements to machine learning library interfaces
pennylane/interfaces
has been refactored. Theexecute_fn
passed to the machine learning framework boundaries is now responsible for converting parameters to NumPy. The gradients module can now handle TensorFlow parameters, but gradient tapes now retain the originaldtype
instead of converting tofloat64
. This may cause instability with finite-difference differentiation andfloat32
parameters. The machine learning boundary functions are now uncoupled from their legacy counterparts. (#4415)qml.interfaces.set_shots
now accepts aShots
object as well asint
โs and tuples ofint
โs. (#4388)Readability improvements and stylistic changes have been made to
pennylane/interfaces/jax_jit_tuple.py
(#4379)
Pulses
A
HardwareHamiltonian
can now be summed withint
orfloat
objects. A sequence ofHardwareHamiltonian
s can now be summed via the builtinsum
. (#4343)qml.pulse.transmon_drive
has been updated in accordance with 1904.06560. In particular, the functional form has been changed from \(\Omega(t)(\cos(\omega_d t + \phi) X - \sin(\omega_d t + \phi) Y)$ to $\Omega(t) \sin(\omega_d t + \phi) Y\). (#4418) (#4465) (#4478) (#4418)
Other improvements
The
qchem
module has been upgraded to use the fermionic operators of thefermi
module. #4336 #4521The calculation of
Sum
,Prod
,SProd
,PauliWord
, andPauliSentence
sparse matrices are orders of magnitude faster. (#4475) (#4272) (#4411)A function called
qml.math.fidelity_statevector
that computes the fidelity between two state vectors has been added. (#4322)qml.ctrl(qml.PauliX)
returns aCNOT
,Toffoli
, orMultiControlledX
operation instead ofControlled(PauliX)
. (#4339)When given a callable,
qml.ctrl
now does its custom pre-processing on all queued operators from the callable. (#4370)The
qchem
functionsprimitive_norm
andcontracted_norm
have been modified to be compatible with higher versions of SciPy. The private function_fac2
for computing double factorials has also been added. #4321tape_expand
now usesOperator.decomposition
instead ofOperator.expand
in order to make more performant choices. (#4355)CI now runs tests with TensorFlow 2.13.0 (#4472)
All tests in CI and pre-commit hooks now enable linting. (#4335)
The default label for a
StatePrepBase
operator is now|ฮจโฉ
. (#4340)Device.default_expand_fn()
has been updated to decomposeqml.StatePrep
operations present in the middle of a provided circuit. (#4437)QNode.construct
has been updated to only apply theqml.defer_measurements
transform if the device does not natively support mid-circuit measurements. (#4516)The application of the
qml.defer_measurements
transform has been moved fromQNode.construct
toqml.Device.batch_transform
to allow more fine-grain control over whendefer_measurements
should be used. (#4432)The label for
ParametrizedEvolution
can display parameters with the requested format as set by the kwargdecimals
. Array-like parameters are displayed in the same format as matrices and stored in the cache. (#4151)
Breaking changes ๐
Applying gradient transforms to broadcasted/batched tapes has been deactivated until it is consistently supported for QNodes as well. (#4480)
Gradient transforms no longer implicitly cast
float32
parameters tofloat64
. Finite difference differentiation withfloat32
parameters may no longer give accurate results. (#4415)The
do_queue
keyword argument inqml.operation.Operator
has been removed. Instead of settingdo_queue=False
, use theqml.QueuingManager.stop_recording()
context. (#4317)Operator.expand
now uses the output ofOperator.decomposition
instead of what it queues. (#4355)The gradients module no longer needs shot information passed to it explicitly, as the shots are on the tapes. (#4448)
qml.StatePrep
has been renamed toqml.StatePrepBase
andqml.QubitStateVector
has been renamed toqml.StatePrep
.qml.operation.StatePrep
andqml.QubitStateVector
are still accessible. (#4450)Support for Python 3.8 has been dropped. (#4453)
MeasurementValue
โs signature has been updated to accept a list ofMidMeasureMP
โs rather than a list of their IDs. (#4446)The
grouping_type
andgrouping_method
keyword arguments have been removed fromqchem.molecular_hamiltonian
. (#4301)zyz_decomposition
andxyx_decomposition
have been removed. Useone_qubit_decomposition
instead. (#4301)LieAlgebraOptimizer
has been removed. UseRiemannianGradientOptimizer
instead. (#4301)Operation.base_name
has been removed. (#4301)QuantumScript.name
has been removed. (#4301)qml.math.reduced_dm
has been removed. Useqml.math.reduce_dm
orqml.math.reduce_statevector
instead. (#4301)The
qml.specs
dictionary no longer supports direct key access to certain keys. (#4301)Instead, these quantities can be accessed as fields of the new
Resources
object saved underspecs_dict["resources"]
:num_operations
is no longer supported, usespecs_dict["resources"].num_gates
num_used_wires
is no longer supported, usespecs_dict["resources"].num_wires
gate_types
is no longer supported, usespecs_dict["resources"].gate_types
gate_sizes
is no longer supported, usespecs_dict["resources"].gate_sizes
depth
is no longer supported, usespecs_dict["resources"].depth
qml.math.purity
,qml.math.vn_entropy
,qml.math.mutual_info
,qml.math.fidelity
,qml.math.relative_entropy
, andqml.math.max_entropy
no longer support state vectors as input. (#4322)The private
QuantumScript._prep
list has been removed, and prep operations now go into the_ops
list. (#4485)
Deprecations ๐
qml.enable_return
andqml.disable_return
have been deprecated. Please avoid callingdisable_return
, as the old return system has been deprecated along with these switch functions. (#4316)qml.qchem.jordan_wigner
has been deprecated. Useqml.jordan_wigner
instead. List input to define the fermionic operator has also been deprecated; the fermionic operators in theqml.fermi
module should be used instead. (#4332)The
qml.RandomLayers.compute_decomposition
keyword argumentratio_imprimitive
will be changed toratio_imprim
to match the call signature of the operation. (#4314)The CV observables
qml.X
andqml.P
have been deprecated. Useqml.QuadX
andqml.QuadP
instead. (#4330)The method
tape.unwrap()
and correspondingUnwrapTape
andUnwrap
classes have been deprecated. Useconvert_to_numpy_parameters
instead. (#4344)The
mode
keyword argument in QNode has been deprecated, as it was only used in the old return system (which has also been deprecated). Please usegrad_on_execution
instead. (#4316)The
QuantumScript.set_parameters
method and theQuantumScript.data
setter have been deprecated. Please useQuantumScript.bind_new_parameters
instead. (#4346)The
__eq__
and__hash__
dunder methods ofOperator
andMeasurementProcess
will now raise warnings to reflect upcoming changes to operator and measurement process equality and hashing. (#4144) (#4454) (#4489) (#4498)The
sampler_seed
argument ofqml.gradients.spsa_grad
has been deprecated, along with a bug fix of the seed-setting behaviour. Instead, thesampler_rng
argument should be set, either to an integer value, which will be used to create a PRNG internally or to a NumPy pseudo-random number generator created vianp.random.default_rng(seed)
. (4165)
Documentation ๐
The
qml.pulse.transmon_interaction
andqml.pulse.transmon_drive
documentation has been updated. #4327qml.ApproxTimeEvolution.compute_decomposition()
now has a code example. (#4354)The documentation for
qml.devices.experimental.Device
has been improved to clarify some aspects of its use. (#4391)Input types and sources for operators in
qml.import_operator
are specified. (#4476)
Bug fixes ๐
qml.Projector
is pickle-able again. (#4452)_copy_and_shift_params
does not cast or convert integral types, just relying on+
and*
โs casting rules in this case. (#4477)Sparse matrix calculations of
SProd
s containing aTensor
are now allowed. When usingTensor.sparse_matrix()
, it is recommended to use thewire_order
keyword argument overwires
. (#4424)op.adjoint
has been replaced withqml.adjoint
inQNSPSAOptimizer
. (#4421)jax.ad
(deprecated) has been replaced byjax.interpreters.ad
. (#4403)metric_tensor
stops accidentally catching errors that stem from flawed wires assignments in the original circuit, leading to recursion errors. (#4328)A warning is now raised if control indicators are hidden when calling
qml.draw_mpl
(#4295)qml.qinfo.purity
now produces correct results with custom wire labels. (#4331)default.qutrit
now supports all qutrit operations used withqml.adjoint
. (#4348)The observable data of
qml.GellMann
now includes its index, allowing correct comparison between instances ofqml.GellMann
, as well as Hamiltonians and Tensors containingqml.GellMann
. (#4366)qml.transforms.merge_amplitude_embedding
now works correctly when theAmplitudeEmbedding
s have a batch dimension. (#4353)The
jordan_wigner
function has been modified to work with Hamiltonians built with an active space. (#4372)When a
style
option is not provided,qml.draw_mpl
uses the current style set fromqml.drawer.use_style
instead ofblack_white
. (#4357)qml.devices.qubit.preprocess.validate_and_expand_adjoint
no longer sets the trainable parameters of the expanded tape. (#4365)qml.default_expand_fn
now selectively expands operations or measurements allowing more operations to be executed in circuits when measuring non-qwc Hamiltonians. (#4401)qml.ControlledQubitUnitary
no longer reportshas_decomposition
asTrue
when it does not really have a decomposition. (#4407)qml.transforms.split_non_commuting
now correctly works on tapes containing bothexpval
andvar
measurements. (#4426)Subtracting a
Prod
from another operator now works as expected. (#4441)The
sampler_seed
argument ofqml.gradients.spsa_grad
has been changed tosampler_rng
. One can either provide an integer, which will be used to create a PRNG internally. Previously, this lead to the same direction being sampled, whennum_directions
is greater than 1. Alternatively, one can provide a NumPy PRNG, which allows reproducibly callingspsa_grad
without getting the same results every time. (4165) (4482)qml.math.get_dtype_name
now works with autograd array boxes. (#4494)The backprop gradient of
qml.math.fidelity
is now correct. (#4380)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Utkarsh Azad, Thomas Bromley, Isaac De Vlugt, Amintor Dusko, Stepan Fomichev, Lillian M. A. Frederiksen, Soran Jahangiri, Edward Jiang, Korbinian Kottmann, Ivana Kureฤiฤ, Christina Lee, Vincent Michaud-Rioux, Romain Moyard, Lee James OโRiordan, Mudit Pandey, Borja Requena, Matthew Silverman, Jay Soni, David Wierichs, Frederik Wilde.
- orphan
Release 0.31.0ยถ
New features since last release
Seamlessly create and combine fermionic operators ๐ฌ
Fermionic operators and arithmetic are now available. (#4191) (#4195) (#4200) (#4201) (#4209) (#4229) (#4253) (#4255) (#4262) (#4278)
There are a couple of ways to create fermionic operators with this new feature:
qml.FermiC
andqml.FermiA
: the fermionic creation and annihilation operators, respectively. These operators are defined by passing the index of the orbital that the fermionic operator acts on. For instance, the operatorsaโบ(0)
anda(3)
are respectively constructed as>>> qml.FermiC(0) aโบ(0) >>> qml.FermiA(3) a(3)
These operators can be composed with (
*
) and linearly combined with (+
and-
) other Fermi operators to create arbitrary fermionic Hamiltonians. Multiplying several Fermi operators together creates an operator that we call a Fermi word:>>> word = qml.FermiC(0) * qml.FermiA(0) * qml.FermiC(3) * qml.FermiA(3) >>> word aโบ(0) a(0) aโบ(3) a(3)
Fermi words can be linearly combined to create a fermionic operator that we call a Fermi sentence:
>>> sentence = 1.2 * word - 0.345 * qml.FermiC(3) * qml.FermiA(3) >>> sentence 1.2 * aโบ(0) a(0) aโบ(3) a(3) - 0.345 * aโบ(3) a(3)
via qml.fermi.from_string: create a fermionic operator that represents multiple creation and annihilation operators being multiplied by each other (a Fermi word).
>>> qml.fermi.from_string('0+ 1- 0+ 1-') aโบ(0) a(1) aโบ(0) a(1) >>> qml.fermi.from_string('0^ 1 0^ 1') aโบ(0) a(1) aโบ(0) a(1)
Fermi words created with
from_string
can also be linearly combined to create a Fermi sentence:>>> word1 = qml.fermi.from_string('0+ 0- 3+ 3-') >>> word2 = qml.fermi.from_string('3+ 3-') >>> sentence = 1.2 * word1 + 0.345 * word2 >>> sentence 1.2 * aโบ(0) a(0) aโบ(3) a(3) + 0.345 * aโบ(3) a(3)
Additionally, any fermionic operator, be it a single fermionic creation/annihilation operator, a Fermi word, or a Fermi sentence, can be mapped to the qubit basis by using qml.jordan_wigner:
>>> qml.jordan_wigner(sentence) ((0.4725+0j)*(Identity(wires=[0]))) + ((-0.4725+0j)*(PauliZ(wires=[3]))) + ((-0.3+0j)*(PauliZ(wires=[0]))) + ((0.3+0j)*(PauliZ(wires=[0]) @ PauliZ(wires=[3])))
Learn how to create fermionic Hamiltonians describing some simple chemical systems by checking out our fermionic operators demo!
Workflow-level resource estimation ๐งฎ
PennyLaneโs Tracker now monitors the resource requirements of circuits being executed by the device. (#4045) (#4110)
Suppose we have a workflow that involves executing circuits with different qubit numbers. We can obtain the resource requirements as a function of the number of qubits by executing the workflow with the
Tracker
context:dev = qml.device("default.qubit", wires=4) @qml.qnode(dev) def circuit(n_wires): for i in range(n_wires): qml.Hadamard(i) return qml.probs(range(n_wires)) with qml.Tracker(dev) as tracker: for i in range(1, 5): circuit(i)
The resource requirements of individual circuits can then be inspected as follows:
>>> resources = tracker.history["resources"] >>> resources[0] wires: 1 gates: 1 depth: 1 shots: Shots(total=None) gate_types: {'Hadamard': 1} gate_sizes: {1: 1} >>> [r.num_wires for r in resources] [1, 2, 3, 4]
Moreover, it is possible to predict the resource requirements without evaluating circuits using the
null.qubit
device, which follows the standard execution pipeline but returns numeric zeros. Consider the following workflow that takes the gradient of a50
-qubit circuit:n_wires = 50 dev = qml.device("null.qubit", wires=n_wires) weight_shape = qml.StronglyEntanglingLayers.shape(2, n_wires) weights = np.random.random(weight_shape, requires_grad=True) @qml.qnode(dev, diff_method="parameter-shift") def circuit(weights): qml.StronglyEntanglingLayers(weights, wires=range(n_wires)) return qml.expval(qml.PauliZ(0)) with qml.Tracker(dev) as tracker: qml.grad(circuit)(weights)
The tracker can be inspected to extract resource requirements without requiring a 50-qubit circuit run:
>>> tracker.totals {'executions': 451, 'batches': 2, 'batch_len': 451} >>> tracker.history["resources"][0] wires: 50 gates: 200 depth: 77 shots: Shots(total=None) gate_types: {'Rot': 100, 'CNOT': 100} gate_sizes: {1: 100, 2: 100}
Custom operations can now be constructed that solely define resource requirements โ an explicit decomposition or matrix representation is not needed. (#4033)
PennyLane is now able to estimate the total resource requirements of circuits that include one or more of these operations, allowing you to estimate requirements for high-level algorithms composed of abstract subroutines.
These operations can be defined by inheriting from ResourcesOperation and overriding the
resources()
method to return an appropriate Resources object:class CustomOp(qml.resource.ResourcesOperation): def resources(self): n = len(self.wires) r = qml.resource.Resources( num_wires=n, num_gates=n ** 2, depth=5, ) return r
>>> wires = [0, 1, 2] >>> c = CustomOp(wires) >>> c.resources() wires: 3 gates: 9 depth: 5 shots: Shots(total=None) gate_types: {} gate_sizes: {}
A quantum circuit that contains
CustomOp
can be created and inspected using qml.specs:dev = qml.device("default.qubit", wires=wires) @qml.qnode(dev) def circ(): qml.PauliZ(wires=0) CustomOp(wires) return qml.state()
>>> specs = qml.specs(circ)() >>> specs["resources"].depth 6
Community contributions from UnitaryHack ๐ค
ParametrizedHamiltonian now has an improved string representation. (#4176)
>>> def f1(p, t): return p[0] * jnp.sin(p[1] * t) >>> def f2(p, t): return p * t >>> coeffs = [2., f1, f2] >>> observables = [qml.PauliX(0), qml.PauliY(0), qml.PauliZ(0)] >>> qml.dot(coeffs, observables) (2.0*(PauliX(wires=[0]))) + (f1(params_0, t)*(PauliY(wires=[0]))) + (f2(params_1, t)*(PauliZ(wires=[0])))
The quantum information module now supports trace distance. (#4181)
Two cases are enabled for calculating the trace distance:
A QNode transform via qml.qinfo.trace_distance:
dev = qml.device('default.qubit', wires=2) @qml.qnode(dev) def circuit(param): qml.RY(param, wires=0) qml.CNOT(wires=[0, 1]) return qml.state()
>>> trace_distance_circuit = qml.qinfo.trace_distance(circuit, circuit, wires0=[0], wires1=[0]) >>> x, y = np.array(0.4), np.array(0.6) >>> trace_distance_circuit((x,), (y,)) 0.047862689546603415
Flexible post-processing via qml.math.trace_distance:
>>> rho = np.array([[0.3, 0], [0, 0.7]]) >>> sigma = np.array([[0.5, 0], [0, 0.5]]) >>> qml.math.trace_distance(rho, sigma) 0.19999999999999998
It is now possible to prepare qutrit basis states with qml.QutritBasisState. (#4185)
wires = range(2) dev = qml.device("default.qutrit", wires=wires) @qml.qnode(dev) def qutrit_circuit(): qml.QutritBasisState([1, 1], wires=wires) qml.TAdd(wires=wires) return qml.probs(wires=1)
>>> qutrit_circuit() array([0., 0., 1.])
A new transform called one_qubit_decomposition has been added to provide a unified interface for decompositions of a single-qubit unitary matrix into sequences of X, Y, and Z rotations. All decompositions simplify the rotations angles to be between
0
and4
pi. (#4210) (#4246)>>> from pennylane.transforms import one_qubit_decomposition >>> U = np.array([[-0.28829348-0.78829734j, 0.30364367+0.45085995j], ... [ 0.53396245-0.10177564j, 0.76279558-0.35024096j]]) >>> one_qubit_decomposition(U, 0, "ZYZ") [RZ(tensor(12.32427531, requires_grad=True), wires=[0]), RY(tensor(1.14938178, requires_grad=True), wires=[0]), RZ(tensor(1.73305815, requires_grad=True), wires=[0])] >>> one_qubit_decomposition(U, 0, "XYX", return_global_phase=True) [RX(tensor(10.84535137, requires_grad=True), wires=[0]), RY(tensor(1.39749741, requires_grad=True), wires=[0]), RX(tensor(0.45246584, requires_grad=True), wires=[0]), (0.38469215914523336-0.9230449299422961j)*(Identity(wires=[0]))]
The
has_unitary_generator
attribute inqml.ops.qubit.attributes
no longer contains operators with non-unitary generators. (#4183)PennyLane Docker builds have been updated to include the latest plugins and interface versions. (#4178)
Extended support for differentiating pulses โ๏ธ
The stochastic parameter-shift gradient method can now be used with hardware-compatible Hamiltonians. (#4132) (#4215)
This new feature generalizes the stochastic parameter-shift gradient transform for pulses (
stoch_pulse_grad
) to support Hermitian generating terms beyond just Pauli words in pulse Hamiltonians, which makes it hardware-compatible.A new differentiation method called qml.gradients.pulse_generator is available, which combines classical processing with the parameter-shift rule for multivariate gates to differentiate pulse programs. Access it in your pulse programs by setting
diff_method=qml.gradients.pulse_generator
. (#4160)qml.pulse.ParametrizedEvolution
now uses batched compressed sparse row (BCSR
) format. This allows for computing Jacobians of the unitary directly even whendense=False
. (#4126)def U(params): H = jnp.polyval * qml.PauliZ(0) # time dependent Hamiltonian Um = qml.evolve(H, dense=False)(params, t=10.) return qml.matrix(Um) params = jnp.array([[0.5]], dtype=complex) jac = jax.jacobian(U, holomorphic=True)(params)
Broadcasting and other tweaks to Torch and Keras layers ๐ฆพ
The
TorchLayer
andKerasLayer
integrations withtorch.nn
andKeras
have been upgraded. Consider the followingTorchLayer
:n_qubits = 2 dev = qml.device("default.qubit", wires=n_qubits) @qml.qnode(dev) def qnode(inputs, weights): qml.AngleEmbedding(inputs, wires=range(n_qubits)) qml.BasicEntanglerLayers(weights, wires=range(n_qubits)) return [qml.expval(qml.PauliZ(wires=i)) for i in range(n_qubits)] n_layers = 6 weight_shapes = {"weights": (n_layers, n_qubits)} qlayer = qml.qnn.TorchLayer(qnode, weight_shapes)
The following features are now available:
Native support for parameter broadcasting. (#4131)
>>> batch_size = 10 >>> inputs = torch.rand((batch_size, n_qubits)) >>> qlayer(inputs) >>> dev.num_executions == 1 True
The ability to draw a
TorchLayer
andKerasLayer
usingqml.draw()
andqml.draw_mpl()
. (#4197)>>> print(qml.draw(qlayer, show_matrices=False)(inputs)) 0: โโญAngleEmbedding(M0)โโญBasicEntanglerLayers(M1)โโค <Z> 1: โโฐAngleEmbedding(M0)โโฐBasicEntanglerLayers(M1)โโค <Z>
Support for
KerasLayer
model saving and clearer instructions onTorchLayer
model saving. (#4149) (#4158)>>> torch.save(qlayer.state_dict(), "weights.pt") # Saving >>> qlayer.load_state_dict(torch.load("weights.pt")) # Loading >>> qlayer.eval()
Hybrid models containing
KerasLayer
orTorchLayer
objects can also be saved and loaded.
Improvements ๐
A more flexible projector
qml.Projector
now accepts a state vector representation, which enables the creation of projectors in any basis. (#4192)dev = qml.device("default.qubit", wires=2) @qml.qnode(dev) def circuit(state): return qml.expval(qml.Projector(state, wires=[0, 1])) zero_state = [0, 0] plusplus_state = np.array([1, 1, 1, 1]) / 2
>>> circuit(zero_state) tensor(1., requires_grad=True) >>> circuit(plusplus_state) tensor(0.25, requires_grad=True)
Do more with qutrits
Three qutrit rotation operators have been added that are analogous to
RX
,RY
, andRZ
:qml.TRX
: an X rotationqml.TRY
: a Y rotationqml.TRZ
: a Z rotation
Qutrit devices now support parameter-shift differentiation. (#2845)
The qchem module
qchem.molecular_hamiltonian()
,qchem.qubit_observable()
,qchem.import_operator()
, andqchem.dipole_moment()
now return an arithmetic operator ifenable_new_opmath()
is active. (#4138) (#4159) (#4189) (#4204)Non-cubic lattice support for all electron resource estimation has been added. (3956)
The
qchem.molecular_hamiltonian()
function has been upgraded to support custom wires for constructing differentiable Hamiltonians. The zero imaginary component of the Hamiltonian coefficients have been removed. (#4050) (#4094)Jordan-Wigner transforms that cache Pauli gate objects have been accelerated. (#4046)
An error is now raised by
qchem.molecular_hamiltonian
when thedhf
method is used for an open-shell system. This duplicates a similar error inqchem.Molecule
but makes it clear that thepyscf
backend can be used for open-shell calculations. (#4058)Updated various qubit tapering methods to support operator arithmetic. (#4252)
Next-generation device API
The new device interface has been integrated with
qml.execute
for autograd, backpropagation, and no differentiation. (#3903)Support for adjoint differentiation has been added to the
DefaultQubit2
device. (#4037)A new function called
measure_with_samples
that returns a sample-based measurement result given a state has been added. (#4083) (#4093) (#4162) (#4254)DefaultQubit2.preprocess
now returns a newExecutionConfig
object with decisions forgradient_method
,use_device_gradient
, andgrad_on_execution
. (#4102)Support for sample-based measurements has been added to the
DefaultQubit2
device. (#4105) (#4114) (#4133) (#4172)The
DefaultQubit2
device now has aseed
keyword argument. (#4120)Added a
dense
keyword toParametrizedEvolution
that allows forcing dense or sparse matrices. (#4079) (#4095) (#4285)Adds the Type variables
pennylane.typing.Result
andpennylane.typing.ResultBatch
for type hinting the result of an execution. (#4018)qml.devices.ExecutionConfig
no longer has ashots
property, as it is now on theQuantumScript
.
It now has ause_device_gradient
property.ExecutionConfig.grad_on_execution = None
indicates a request for"best"
, instead of a string. (#4102)The new device interface for Jax has been integrated with
qml.execute
. (#4137)The new device interface is now integrated with
qml.execute
for Tensorflow. (#4169)The experimental device
DefaultQubit2
now supportsqml.Snapshot
. (#4193)The experimental device interface is integrated with the
QNode
. (#4196)The new device interface in integrated with
qml.execute
for Torch. (#4257)
Handling shots
QuantumScript
now has ashots
property, allowing shots to be tied to executions instead of devices. (#4067) (#4103) (#4106) (#4112)Several Python built-in functions are now properly defined for instances of the
Shots
class.print
: printingShots
instances is now human-readablestr
: convertingShots
instances to human-readable strings==
: equating two differentShots
instanceshash
: obtaining the hash values ofShots
instances
qml.devices.ExecutionConfig
no longer has ashots
property, as it is now on theQuantumScript
. It now has ause_device_gradient
property.ExecutionConfig.grad_on_execution = None
indicates a request for"best"
instead of a string. (#4102)QuantumScript.shots
has been integrated with QNodes so that shots are placed on theQuantumScript
duringQNode
construction. (#4110)The
gradients
module has been updated to use the newShots
object internally (#4152)
Operators
qml.prod
now accepts a single quantum function input for creating newProd
operators. (#4011)DiagonalQubitUnitary
now decomposes intoRZ
,IsingZZ
andMultiRZ
gates instead of aQubitUnitary
operation with a dense matrix. (#4035)All objects being queued in an
AnnotatedQueue
are now wrapped so thatAnnotatedQueue
is not dependent on the has of any operators or measurement processes. (#4087)A
dense
keyword toParametrizedEvolution
that allows forcing dense or sparse matrices has been added. (#4079) (#4095)Added a new function
qml.ops.functions.bind_new_parameters
that creates a copy of an operator with new parameters without mutating the original operator. (#4113) (#4256)qml.CY
has been moved fromqml.ops.qubit.non_parametric_ops
toqml.ops.op_math.controlled_ops
and now inherits fromqml.ops.op_math.ControlledOp
. (#4116)qml.CZ
now inherits from theControlledOp
class and supports exponentiation to arbitrary powers withpow
, which is no longer limited to integers. It also supportssparse_matrix
anddecomposition
representations. (#4117)The construction of the Pauli representation for the
Sum
class is now faster. (#4142)qml.drawer.drawable_layers.drawable_layers
andqml.CircuitGraph
have been updated to not rely onOperator
equality or hash to work correctly. (#4143)
Other improvements
A transform dispatcher and program have been added. (#4109) (#4187)
Reduced density matrix functionality has been added via
qml.math.reduce_dm
andqml.math.reduce_statevector
. Both functions have broadcasting support. (#4173)The following functions in
qml.qinfo
now support parameter broadcasting:reduced_dm
purity
vn_entropy
mutual_info
fidelity
relative_entropy
trace_distance
The following functions in
qml.math
now support parameter broadcasting:purity
vn_entropy
mutual_info
fidelity
relative_entropy
max_entropy
sqrt_matrix
pulse.ParametrizedEvolution
now raises an error if the number of input parameters does not match the number of parametrized coefficients in theParametrizedHamiltonian
that generates it. An exception is made forHardwareHamiltonian
s which are not checked. (#4216)The default value for the
show_matrices
keyword argument in all drawing methods is nowTrue
. This allows for quick insights into broadcasted tapes, for example. (#3920)Type variables for
qml.typing.Result
andqml.typing.ResultBatch
have been added for type hinting the result of an execution. (#4108)The Jax-JIT interface now uses symbolic zeros to determine trainable parameters. (4075)
A new function called
pauli.pauli_word_prefactor()
that extracts the prefactor for a given Pauli word has been added. (#4164)Variable-length argument lists of functions and methods in some docstrings is now more clear. (#4242)
qml.drawer.drawable_layers.drawable_layers
andqml.CircuitGraph
have been updated to not rely onOperator
equality or hash to work correctly. (#4143)Drawing mid-circuit measurements connected by classical control signals to conditional operations is now possible. (#4228)
The autograd interface now submits all required tapes in a single batch on the backward pass. (#4245)
Breaking changes ๐
The default value for the
show_matrices
keyword argument in all drawing methods is nowTrue
. This allows for quick insights into broadcasted tapes, for example. (#3920)DiagonalQubitUnitary
now decomposes intoRZ
,IsingZZ
, andMultiRZ
gates rather than aQubitUnitary
. (#4035)Jax trainable parameters are now
Tracer
instead ofJVPTracer
. It is not always the right definition for the JIT interface, but we update them in the custom JVP using symbolic zeros. (4075)The experimental Device interface
qml.devices.experimental.Device
now requires that thepreprocess
method also returns anExecutionConfig
object. This allows the device to choose what"best"
means for various hyperparameters likegradient_method
andgrad_on_execution
. (#4007) (#4102)Gradient transforms with Jax no longer support
argnum
. Useargnums
instead. (#4076)qml.collections
,qml.op_sum
, andqml.utils.sparse_hamiltonian
have been removed. (#4071)The
pennylane.transforms.qcut
module now uses(op, id(op))
as nodes in directed multigraphs that are used within the circuit cutting workflow instead ofop
. This change removes the dependency of the module on the hash of operators. (#4227)Operator.data
now returns atuple
instead of alist
. (#4222)The pulse differentiation methods,
pulse_generator
andstoch_pulse_grad
, now raise an error when they are applied to a QNode directly. Instead, use differentiation via a JAX entry point (jax.grad
,jax.jacobian
, โฆ). (#4241)
Deprecations ๐
LieAlgebraOptimizer
has been renamed toRiemannianGradientOptimizer
. [(#4153)(https://github.com/PennyLaneAI/pennylane/pull/4153)]Operation.base_name
has been deprecated. Please useOperation.name
ortype(op).__name__
instead.QuantumScript
โsname
keyword argument and property have been deprecated. This also affectsQuantumTape
andOperationRecorder
. (#4141)The
qml.grouping
module has been removed. Its functionality has been reorganized in theqml.pauli
module.The public methods of
DefaultQubit
are pending changes to follow the new device API, as used inDefaultQubit2
. Warnings have been added to the docstrings to reflect this. (#4145)qml.math.reduced_dm
has been deprecated. Please useqml.math.reduce_dm
orqml.math.reduce_statevector
instead. (#4173)qml.math.purity
,qml.math.vn_entropy
,qml.math.mutual_info
,qml.math.fidelity
,qml.math.relative_entropy
, andqml.math.max_entropy
no longer support state vectors as input. Please callqml.math.dm_from_state_vector
on the input before passing to any of these functions. (#4186)The
do_queue
keyword argument inqml.operation.Operator
has been deprecated. Instead of settingdo_queue=False
, use theqml.QueuingManager.stop_recording()
context. (#4148)zyz_decomposition
andxyx_decomposition
are now deprecated in favour ofone_qubit_decomposition
. (#4230)
Documentation ๐
The documentation is updated to construct
QuantumTape
upon initialization instead of with queuing. (#4243)The docstring for
qml.ops.op_math.Pow.__new__
is now complete and it has been updated along withqml.ops.op_math.Adjoint.__new__
. (#4231)The docstring for
qml.grad
now states that it should be used with the Autograd interface only. (#4202)The description of
mult
in theqchem.Molecule
docstring now correctly states the value ofmult
that is supported. (#4058)
Bug Fixes ๐
Fixed adjoint jacobian results with
grad_on_execution=False
in the JAX-JIT interface. (4217)Fixed the matrix of
SProd
when the coefficient is tensorflow and the target matrix is notcomplex128
. (#4249)Fixed a bug where
stoch_pulse_grad
would ignore prefactors of rescaled Pauli words in the generating terms of a pulse Hamiltonian. (4156)Fixed a bug where the wire ordering of the
wires
argument toqml.density_matrix
was not taken into account. (#4072)A patch in
interfaces/autograd.py
that checks for thestrawberryfields.gbs
device has been removed. That device is pinned to PennyLane <= v0.29.0, so that patch is no longer necessary. (#4089)qml.pauli.are_identical_pauli_words
now treats all identities as equal. Identity terms on Hamiltonians with non-standard wire orders are no longer eliminated. (#4161)qml.pauli_sentence()
is now compatible with empty Hamiltoniansqml.Hamiltonian([], [])
. (#4171)Fixed a bug with Jax where executing multiple tapes with
gradient_fn="device"
would fail. (#4190)A more meaningful error message is raised when broadcasting with adjoint differentiation on
DefaultQubit
. (#4203)The
has_unitary_generator
attribute inqml.ops.qubit.attributes
no longer contains operators with non-unitary generators. (#4183)Fixed a bug where
op = qml.qsvt()
was incorrect up to a global phase when usingconvention="Wx""
andqml.matrix(op)
. (#4214)Fixed a buggy calculation of the angle in
xyx_decomposition
that causes it to give an incorrect decomposition. Anif
conditional was intended to prevent divide by zero errors, but the division was by the sine of the argument. So, any multiple of $pi$ should trigger the conditional, but it was only checking if the argument was 0. Example:qml.Rot(2.3, 2.3, 2.3)
(#4210)Fixed bug that caused
ShotAdaptiveOptimizer
to truncate dimensions of parameter-distributed shots during optimization. (#4240)Sum
observables can now have trainable parameters. (#4251) (#4275)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Venkatakrishnan AnushKrishna, Utkarsh Azad, Thomas Bromley, Isaac De Vlugt, Lillian M. A. Frederiksen, Emiliano Godinez Ramirez Nikhil Harle Soran Jahangiri, Edward Jiang, Korbinian Kottmann, Christina Lee, Vincent Michaud-Rioux, Romain Moyard, Tristan Nemoz, Mudit Pandey, Manul Patel, Borja Requena, Modjtaba Shokrian-Zini, Mainak Roy, Matthew Silverman, Jay Soni, Edward Thomas, David Wierichs, Frederik Wilde.
- orphan
Release 0.30.0ยถ
New features since last release
Pulse programming on hardware โ๏ธ๐ฌ
Support for loading time-dependent Hamiltonians that are compatible with quantum hardware has been added, making it possible to load a Hamiltonian that describes an ensemble of Rydberg atoms or a collection of transmon qubits. (#3749) (#3911) (#3930) (#3936) (#3966) (#3987) (#4021) (#4040)
Rydberg atoms are the foundational unit for neutral atom quantum computing. A Rydberg-system Hamiltonian can be constructed from a drive term โ
qml.pulse.rydberg_drive
โ and an interaction term โqml.pulse.rydberg_interaction
:from jax import numpy as jnp atom_coordinates = [[0, 0], [0, 4], [4, 0], [4, 4]] wires = [0, 1, 2, 3] amplitude = lambda p, t: p * jnp.sin(jnp.pi * t) phase = jnp.pi / 2 detuning = 3 * jnp.pi / 4 H_d = qml.pulse.rydberg_drive(amplitude, phase, detuning, wires) H_i = qml.pulse.rydberg_interaction(atom_coordinates, wires) H = H_d + H_i
The time-dependent Hamiltonian
H
can be used in a PennyLane pulse-level differentiable circuit:dev = qml.device("default.qubit.jax", wires=wires) @qml.qnode(dev, interface="jax") def circuit(params): qml.evolve(H)(params, t=[0, 10]) return qml.expval(qml.PauliZ(0))
>>> params = jnp.array([2.4]) >>> circuit(params) Array(0.6316659, dtype=float32) >>> import jax >>> jax.grad(circuit)(params) Array([1.3116529], dtype=float32)
The qml.pulse page contains additional details. Check out our release blog post for a demonstration of how to perform the execution on actual hardware!
A pulse-level circuit can now be differentiated using a stochastic parameter-shift method. (#3780) (#3900) (#4000) (#4004)
The new qml.gradient.stoch_pulse_grad differentiation method unlocks stochastic-parameter-shift differentiation for pulse-level circuits. The current version of this new method is restricted to Hamiltonians composed of parametrized Pauli words, but future updates to extend to parametrized Pauli sentences can allow this method to be compatible with hardware-based systems such as an ensemble of Rydberg atoms.
This method can be activated by setting
diff_method
to qml.gradient.stoch_pulse_grad:>>> dev = qml.device("default.qubit.jax", wires=2) >>> sin = lambda p, t: jax.numpy.sin(p * t) >>> ZZ = qml.PauliZ(0) @ qml.PauliZ(1) >>> H = 0.5 * qml.PauliX(0) + qml.pulse.constant * ZZ + sin * qml.PauliX(1) >>> @qml.qnode(dev, interface="jax", diff_method=qml.gradients.stoch_pulse_grad) >>> def ansatz(params): ... qml.evolve(H)(params, (0.2, 1.)) ... return qml.expval(qml.PauliY(1)) >>> params = [jax.numpy.array(0.4), jax.numpy.array(1.3)] >>> jax.grad(ansatz)(params) [Array(0.16921353, dtype=float32, weak_type=True), Array(-0.2537478, dtype=float32, weak_type=True)]
Quantum singular value transformation ๐โก๏ธ๐ฆ
PennyLane now supports the quantum singular value transformation (QSVT), which describes how a quantum circuit can be constructed to apply a polynomial transformation to the singular values of an input matrix. (#3756) (#3757) (#3758) (#3905) (#3909) (#3926) (#4023)
Consider a matrix
A
along with a vectorangles
that describes the target polynomial transformation. Theqml.qsvt
function creates a corresponding circuit:dev = qml.device("default.qubit", wires=2) A = np.array([[0.1, 0.2], [0.3, 0.4]]) angles = np.array([0.1, 0.2, 0.3]) @qml.qnode(dev) def example_circuit(A): qml.qsvt(A, angles, wires=[0, 1]) return qml.expval(qml.PauliZ(wires=0))
This circuit is composed of
qml.BlockEncode
andqml.PCPhase
operations.>>> example_circuit(A) tensor(0.97777078, requires_grad=True) >>> print(example_circuit.qtape.expand(depth=1).draw(decimals=2)) 0: โโญโ_ฯ(0.30)โโญBlockEncode(M0)โโญโ_ฯ(0.20)โโญBlockEncode(M0)โ โโญโ_ฯ(0.10)โโค <Z> 1: โโฐโ_ฯ(0.30)โโฐBlockEncode(M0)โโฐโ_ฯ(0.20)โโฐBlockEncode(M0)โ โโฐโ_ฯ(0.10)โโค
The qml.qsvt function creates a circuit that is targeted at simulators due to the use of matrix-based operations. For advanced users, you can use the operation-based
qml.QSVT
template to perform the transformation with a custom choice of unitary and projector operations, which may be hardware compatible if a decomposition is provided.The QSVT is a complex but powerful transformation capable of generalizing important algorithms like amplitude amplification. Stay tuned for a demo in the coming few weeks to learn more!
Intuitive QNode returns โฉ๏ธ
An updated QNode return system has been introduced. PennyLane QNodes now return exactly what you tell them to! ๐ (#3957) (#3969) (#3946) (#3913) (#3914) (#3934)
This was an experimental feature introduced in version 0.25 of PennyLane that was enabled via
qml.enable_return()
. Now, itโs the default return system. Letโs see how it works.Consider the following circuit:
import pennylane as qml dev = qml.device("default.qubit", wires=1) @qml.qnode(dev) def circuit(x): qml.RX(x, wires=0) return qml.expval(qml.PauliZ(0)), qml.probs(0)
In version 0.29 and earlier of PennyLane,
circuit()
would return a single length-3 array:>>> circuit(0.5) tensor([0.87758256, 0.93879128, 0.06120872], requires_grad=True)
In versions 0.30 and above,
circuit()
returns a length-2 tuple containing the expectation value and probabilities separately:>>> circuit(0.5) (tensor(0.87758256, requires_grad=True), tensor([0.93879128, 0.06120872], requires_grad=True))
You can find more details about this change, along with help and troubleshooting tips to solve any issues. If you still have questions, comments, or concerns, we encourage you to post on the PennyLane discussion forum.
A bunch of performance tweaks ๐๐จ
Single-qubit operations that have multi-qubit control can now be decomposed more efficiently using fewer CNOT gates. (#3851)
Three decompositions from arXiv:2302.06377 are provided and compare favourably to the already-available
qml.ops.ctrl_decomp_zyz
:wires = [0, 1, 2, 3, 4, 5] control_wires = wires[1:] @qml.qnode(qml.device('default.qubit', wires=6)) def circuit(): with qml.QueuingManager.stop_recording(): # the decomposition does not un-queue the target target = qml.RX(np.pi/2, wires=0) qml.ops.ctrl_decomp_bisect(target, (1, 2, 3, 4, 5)) return qml.state() print(qml.draw(circuit, expansion_strategy="device")())
0: โโHโโญXโโU(M0)โโญXโโU(M0)โ โโญXโโU(M0)โโญXโโU(M0)โ โโHโโค State 1: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค State 2: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค State 3: โโโโโฐโโโโโโโโโโโโโโโโโโโโโฐโโโโโโโโโโโโโโโโโโโโโโโโค State 4: โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค State 5: โโโโโโโโโโโโโโโฐโโโโโโโโโโโโโโโโโโโโโฐโโโโโโโโโโโโโโค State
A new decomposition to
qml.SingleExcitation
has been added that halves the number of CNOTs required. (3976)>>> qml.SingleExcitation.compute_decomposition(1.23, wires=(0,1)) [Adjoint(T(wires=[0])), Hadamard(wires=[0]), S(wires=[0]), Adjoint(T(wires=[1])), Adjoint(S(wires=[1])), Hadamard(wires=[1]), CNOT(wires=[1, 0]), RZ(-0.615, wires=[0]), RY(0.615, wires=[1]), CNOT(wires=[1, 0]), Adjoint(S(wires=[0])), Hadamard(wires=[0]), T(wires=[0]), Hadamard(wires=[1]), S(wires=[1]), T(wires=[1])]
The adjoint differentiation method can now be more efficient, avoiding the decomposition of operations that can be differentiated directly. Any operation that defines a
generator()
can be differentiated with the adjoint method. (#3874)For example, in version 0.29 the
qml.CRY
operation would be decomposed when calculating the adjoint-method gradient. Executing the code below shows that this decomposition no longer takes place in version 0.30 andqml.CRY
is differentiated directly:import jax from jax import numpy as jnp def compute_decomposition(self, phi, wires): print("A decomposition has been performed!") decomp_ops = [ qml.RY(phi / 2, wires=wires[1]), qml.CNOT(wires=wires), qml.RY(-phi / 2, wires=wires[1]), qml.CNOT(wires=wires), ] return decomp_ops qml.CRY.compute_decomposition = compute_decomposition dev = qml.device("default.qubit", wires=2) @qml.qnode(dev, diff_method="adjoint") def circuit(phi): qml.Hadamard(wires=0) qml.CRY(phi, wires=[0, 1]) return qml.expval(qml.PauliZ(1)) phi = jnp.array(0.5) jax.grad(circuit)(phi)
Derivatives are computed more efficiently when using
jax.jit
with gradient transforms; the trainable parameters are now set correctly instead of every parameter having to be set as trainable. (#3697)In the circuit below, only the derivative with respect to parameter
b
is now calculated:dev = qml.device("default.qubit", wires=2) @qml.qnode(dev, interface="jax-jit") def circuit(a, b): qml.RX(a, wires=0) qml.RY(b, wires=0) qml.CNOT(wires=[0, 1]) return qml.expval(qml.PauliZ(0)) a = jnp.array(0.4) b = jnp.array(0.5) jac = jax.jacobian(circuit, argnums=[1]) jac_jit = jax.jit(jac) jac_jit(a, b) assert len(circuit.tape.trainable_params) == 1
Improvements ๐
Next-generation device API
In this release and future releases, we will be making changes to our device API with the goal in mind to make developing plugins much easier for developers and unlock new device capabilities. Users shouldnโt yet feel any of these changes when using PennyLane, but here is what has changed this release:
Several functions in
devices/qubit
have been added or improved:sample_state
: returns a series of samples based on a given state vector and a number of shots. (#3720)simulate
: supports measuring expectation values of large observables such asqml.Hamiltonian
,qml.SparseHamiltonian
, andqml.Sum
. (#3759)apply_operation
: supports broadcasting. (#3852)adjoint_jacobian
: supports adjoint differentiation in the new qubit state-vector device. (#3790)
qml.devices.qubit.preprocess
now allows circuits with non-commuting observables. (#3857)qml.devices.qubit.measure
now computes the expectation values ofHamiltonian
andSum
in a backpropagation-compatible way. (#3862)
Pulse programming
Here are the functions, classes, and more that were added or improved to facilitate simulating ensembles of Rydberg atoms: (#3749) (#3911) (#3930) (#3936) (#3966) (#3987) (#3889) (#4021)
HardwareHamiltonian
: an internal class that contains additional information about pulses and settings.rydberg_interaction
: a user-facing function that returns aHardwareHamiltonian
containing the Hamiltonian of the interaction of all the Rydberg atoms.transmon_interaction
: a user-facing function for constructing the Hamiltonian that describes the circuit QED interaction Hamiltonian of superconducting transmon systems.drive
: a user-facing function function that returns aParametrizedHamiltonian
(HardwareHamiltonian
) containing the Hamiltonian of the interaction between a driving electro-magnetic field and a group of qubits.rydberg_drive
: a user-facing function that returns aParametrizedHamiltonian
(HardwareHamiltonian
) containing the Hamiltonian of the interaction between a driving laser field and a group of Rydberg atoms.max_distance
: a keyword argument added toqml.pulse.rydberg_interaction
to allow for the removal of negligible contributions from atoms beyondmax_distance
from each other.
ParametrizedEvolution
now takes two new Boolean keyword arguments:return_intermediate
andcomplementary
. They allow computing intermediate time evolution matrices. (#3900)Activating
return_intermediate
will return intermediate time evolution steps, for example for the matrix of the Operation, or of a quantum circuit when used in a QNode. Activatingcomplementary
will make these intermediate steps be the remaining time evolution complementary to the output forcomplementary=False
. See the docstring for details.Hardware-compatible pulse sequence gradients with
qml.gradient.stoch_pulse_grad
can now be calculated faster using the new keyword argumentuse_broadcasting
. Executing aParametrizedEvolution
that returns intermediate evolutions has increased performance using the state vector ODE solver, as well. (#4000) (#4004)
Intuitive QNode returns
The QNode keyword argument
mode
has been replaced by the booleangrad_on_execution
. (#3969)The
"default.gaussian"
device and parameter-shift CV both support the new return system, but only for single measurements. (#3946)Keras and Torch NN modules are now compatible with the new return type system. (#3913) (#3914)
DefaultQutrit
now supports the new return system. (#3934)
Performance improvements
The efficiency of
tapering()
,tapering_hf()
andclifford()
have been improved. (3942)The peak memory requirements of
tapering()
andtapering_hf()
have been improved when used for larger observables. (3977)Pauli arithmetic has been updated to convert to a Hamiltonian more efficiently. (#3939)
Operator
has a new Boolean attributehas_generator
. It returns whether or not theOperator
has agenerator
defined.has_generator
is used inqml.operation.has_gen
, which improves its performance and extends differentiation support. (#3875)The performance of
CompositeOp
has been significantly improved now that it overrides determining whether it is being used with a batch of parameters (seeOperator._check_batching
).Hamiltonian
also now overrides this, but it does nothing since it does not support batching. (#3915)The performance of a
Sum
operator has been significantly improved now thatis_hermitian
checks that all coefficients are real if the operator has a pre-computed Pauli representation. (#3915)The
coefficients
function and thevisualize
submodule of theqml.fourier
module now allow assigning different degrees for different parameters of the input function. (#3005)Previously, the arguments
degree
andfilter_threshold
toqml.fourier.coefficients
were expected to be integers. Now, they can be a sequences of integers with one integer per function parameter (i.e.len(degree)==n_inputs
), resulting in a returned array with shape(2*degrees[0]+1,..., 2*degrees[-1]+1)
. The functions inqml.fourier.visualize
accordingly accept such arrays of coefficients.
Other improvements
A
Shots
class has been added to themeasurements
module to hold shot-related data. (#3682)The custom JVP rules in PennyLane also now support non-scalar and mixed-shape tape parameters as well as multi-dimensional tape return types, like broadcasted
qml.probs
, for example. (#3766)The
qchem.jordan_wigner
function has been extended to support more fermionic operator orders. (#3754) (#3751)The
AdaptiveOptimizer
has been updated to use non-default user-defined QNode arguments. (#3765)Operators now use
TensorLike
types dunder methods. (#3749)qml.QubitStateVector.state_vector
now supports broadcasting. (#3852)qml.SparseHamiltonian
can now be applied to any wires in a circuit rather than being restricted to all wires in the circuit. (#3888)Operators can now be divided by scalars with
/
with the addition of theOperation.__truediv__
dunder method. (#3749)Printing an instance of
MutualInfoMP
now displays the distribution of the wires between the two subsystems. (#3898)Operator.num_wires
has been changed from an abstract value toAnyWires
. (#3919)qml.transforms.sum_expand
is not run inDevice.batch_transform
if the device supportsSum
observables. (#3915)The type of
n_electrons
inqml.qchem.Molecule
has been set toint
. (#3885)Explicit errors have been added to
QutritDevice
ifclassical_shadow
orshadow_expval
is measured. (#3934)QubitDevice
now defines the private_get_diagonalizing_gates(circuit)
method and uses it when executing circuits. This allows devices that inherit fromQubitDevice
to override and customize their definition of diagonalizing gates. (#3938)retworkx
has been renamed torustworkx
to accommodate the change in the package name. (#3975)Exp
,Sum
,Prod
, andSProd
operator data is now a flat list instead of nested. (#3958) (#3983)qml.transforms.convert_to_numpy_parameters
has been added to convert a circuit with interface-specific parameters to one with only numpy parameters. This transform is designed to replaceqml.tape.Unwrap
. (#3899)qml.operation.WiresEnum.AllWires
is now -2 instead of 0 to avoid the ambiguity betweenop.num_wires = 0
andop.num_wires = AllWires
. (#3978)Execution code has been updated to use the new
qml.transforms.convert_to_numpy_parameters
instead ofqml.tape.Unwrap
. (#3989)A sub-routine of
expand_tape
has been converted intoqml.tape.tape.rotations_and_diagonal_measurements
, a helper function that computes rotations and diagonal measurements for a tape with measurements with overlapping wires. (#3912)Various operators and templates have been updated to ensure that their decompositions only return lists of operators. (#3243)
The
qml.operation.enable_new_opmath
toggle has been introduced to cause dunder methods to return arithmetic operators instead of aHamiltonian
orTensor
. (#4008)>>> type(qml.PauliX(0) @ qml.PauliZ(1)) <class 'pennylane.operation.Tensor'> >>> qml.operation.enable_new_opmath() >>> type(qml.PauliX(0) @ qml.PauliZ(1)) <class 'pennylane.ops.op_math.prod.Prod'> >>> qml.operation.disable_new_opmath() >>> type(qml.PauliX(0) @ qml.PauliZ(1)) <class 'pennylane.operation.Tensor'>
A new data class called
Resources
has been added to store resources like the number of gates and circuit depth throughout a quantum circuit. (#3981)A new function called
_count_resources()
has been added to count the resources required when executing aQuantumTape
for a given number of shots. (#3996)QuantumScript.specs
has been modified to make use of the newResources
class. This also modifies the output ofqml.specs()
. (#4015)A new class called
ResourcesOperation
has been added to allow users to define operations with custom resource information. (#4026)For example, users can define a custom operation by inheriting from this new class:
>>> class CustomOp(qml.resource.ResourcesOperation): ... def resources(self): ... return qml.resource.Resources(num_wires=1, num_gates=2, ... gate_types={"PauliX": 2}) ... >>> CustomOp(wires=1) CustomOp(wires=[1])
Then, we can track and display the resources of the workflow using
qml.specs()
:>>> dev = qml.device("default.qubit", wires=[0,1]) >>> @qml.qnode(dev) ... def circ(): ... qml.PauliZ(wires=0) ... CustomOp(wires=1) ... return qml.state() ... >>> print(qml.specs(circ)()['resources']) wires: 2 gates: 3 depth: 1 shots: 0 gate_types: {'PauliZ': 1, 'PauliX': 2}
MeasurementProcess.shape
now accepts aShots
object as one of its arguments to reduce exposure to unnecessary execution details. (#4012)
Breaking changes ๐
The
seed_recipes
argument has been removed fromqml.classical_shadow
andqml.shadow_expval
. (#4020)The tape method
get_operation
has an updated signature. (#3998)Both JIT interfaces are no longer compatible with JAX
>0.4.3
(we raise an error for those versions). (#3877)An operation that implements a custom
generator
method, but does not always return a valid generator, also has to implement ahas_generator
property that reflects in which scenarios a generator will be returned. (#3875)Trainable parameters for the Jax interface are the parameters that are
JVPTracer
, defined by settingargnums
. Previously, all JAX tracers, including those used for JIT compilation, were interpreted to be trainable. (#3697)The keyword argument
argnums
is now used for gradient transforms using Jax instead ofargnum
.argnum
is automatically converted toargnums
when using Jax and will no longer be supported in v0.31 of PennyLane. (#3697) (#3847)qml.OrbitalRotation
and, consequently,qml.GateFabric
are now more consistent with the interleaved Jordan-Wigner ordering. Previously, they were consistent with the sequential Jordan-Wigner ordering. (#3861)Some
MeasurementProcess
classes can now only be instantiated with arguments that they will actually use. For example, you can no longer createStateMP(qml.PauliX(0))
orPurityMP(eigvals=(-1,1), wires=Wires(0))
. (#3898)Exp
,Sum
,Prod
, andSProd
operator data is now a flat list, instead of nested. (#3958) (#3983)qml.tape.tape.expand_tape
and, consequentially,QuantumScript.expand
no longer update the input tape with rotations and diagonal measurements. Note that the newly expanded tape that is returned will still have the rotations and diagonal measurements. (#3912)qml.Evolution
now initializes the coefficient with a factor of-1j
instead of1j
. (#4024)
Deprecations ๐
Nothing for this release!
Documentation ๐
The documentation of
QubitUnitary
andDiagonalQubitUnitary
was clarified regarding the parameters of the operations. (#4031)A typo has been corrected in the documentation for the introduction to
inspecting_circuits
andchemistry
. (#3844)Usage Details
andTheory
sections have been separated in the documentation forqml.qchem.taper_operation
. (3977)
Bug fixes ๐
ctrl_decomp_bisect
andctrl_decomp_zyz
are no longer used by default when decomposing controlled operations due to the presence of a global phase difference in the zyz decomposition of some target operators. (#4065)Fixed a bug where
qml.math.dot
returned a numpy array instead of an autograd array, breaking autograd derivatives in certain circumstances. (#4019)Operators now cast a
tuple
to annp.ndarray
as well aslist
. (#4022)Fixed a bug where
qml.ctrl
with parametric gates was incompatible with PyTorch tensors on GPUs. (#4002)Fixed a bug where the broadcast expand results were stacked along the wrong axis for the new return system. (#3984)
A more informative error message is raised in
qml.jacobian
to explain potential problems with the new return types specification. (#3997)Fixed a bug where calling
Evolution.generator
withcoeff
being a complex ArrayBox raised an error. (#3796)MeasurementProcess.hash
now uses the hash property of the observable. The property now depends on all properties that affect the behaviour of the object, such asVnEntropyMP.log_base
or the distribution of wires between the two subsystems inMutualInfoMP
. (#3898)The enum
measurements.Purity
has been added so thatPurityMP.return_type
is defined.str
andrepr
forPurityMP
are also now defined. (#3898)Sum.hash
andProd.hash
have been changed slightly to work with non-numeric wire labels.sum_expand
should now return correct results and not treat some products as the same operation. (#3898)Fixed bug where the coefficients where not ordered correctly when summing a
ParametrizedHamiltonian
with other operators. (#3749) (#3902)The metric tensor transform is now fully compatible with Jax and therefore users can provide multiple parameters. (#3847)
qml.math.ndim
andqml.math.shape
are now registered for built-ins and autograd to accomodate Autoray 0.6.1. #3864Ensured that
qml.data.load
returns datasets in a stable and expected order. (#3856)The
qml.equal
function now handles comparisons ofParametrizedEvolution
operators. (#3870)qml.devices.qubit.apply_operation
catches thetf.errors.UnimplementedError
that occurs whenPauliZ
orCNOT
gates are applied to a large (>8 wires) tensorflow state. When that occurs, the logic falls back to the tensordot logic instead. (#3884)Fixed parameter broadcasting support with
qml.counts
in most cases and introduced explicit errors otherwise. (#3876)An error is now raised if a QNode with Jax-jit in use returns
counts
while having trainable parameters (#3892)A correction has been added to the reference values in
test_dipole_of
to account for small changes (~2e-8
) in the computed dipole moment values resulting from the new PySCF 2.2.0 release. (#3908)SampleMP.shape
is now correct when sampling only occurs on a subset of the device wires. (#3921)An issue has been fixed in
qchem.Molecule
to allow basis sets other than the hard-coded ones to be used in theMolecule
class. (#3955)Fixed bug where all devices that inherit from
DefaultQubit
claimed to supportParametrizedEvolution
. Now, onlyDefaultQubitJax
supports the operator, as expected. (#3964)Ensured that parallel
AnnotatedQueues
do not queue each otherโs contents. (#3924)Added a
map_wires
method toPauliWord
andPauliSentence
, and ensured that operators call it in their respectivemap_wires
methods if they have a Pauli rep. (#3985)Fixed a bug when a
Tensor
is multiplied by aHamiltonian
or vice versa. (#4036)
Contributors โ๏ธ
This release contains contributions from (in alphabetical order):
Komi Amiko, Utkarsh Azad, Thomas Bromley, Isaac De Vlugt, Olivia Di Matteo, Lillian M. A. Frederiksen, Diego Guala, Soran Jahangiri, Korbinian Kottmann, Christina Lee, Vincent Michaud-Rioux, Albert Mitjans Coma, Romain Moyard, Lee J. OโRiordan, Mudit Pandey, Matthew Silverman, Jay Soni, David Wierichs.
- orphan
Release 0.29.0ยถ
New features since last release
Pulse programming ๐
Support for creating pulse-based circuits that describe evolution under a time-dependent Hamiltonian has now been added, as well as the ability to execute and differentiate these pulse-based circuits on simulator. (#3586) (#3617) (#3645) (#3652) (#3665) (#3673) (#3706) (#3730)
A time-dependent Hamiltonian can be created using
qml.pulse.ParametrizedHamiltonian
, which holds information representing a linear combination of operators with parametrized coefficents and can be constructed as follows:from jax import numpy as jnp f1 = lambda p, t: p * jnp.sin(t) * (t - 1) f2 = lambda p, t: p[0] * jnp.cos(p[1]* t ** 2) XX = qml.PauliX(0) @ qml.PauliX(1) YY = qml.PauliY(0) @ qml.PauliY(1) ZZ = qml.PauliZ(0) @ qml.PauliZ(1) H = 2 * ZZ + f1 * XX + f2 * YY
>>> H ParametrizedHamiltonian: terms=3 >>> p1 = jnp.array(1.2) >>> p2 = jnp.array([2.3, 3.4]) >>> H((p1, p2), t=0.5) (2*(PauliZ(wires=[0]) @ PauliZ(wires=[1]))) + ((-0.2876553231625218*(PauliX(wires=[0]) @ PauliX(wires=[1]))) + (1.517961235535459*(PauliY(wires=[0]) @ PauliY(wires=[1]))))
The time-dependent Hamiltonian can be used within a circuit with
qml.evolve
:def pulse_circuit(params, time): qml.evolve(H)(params, time) return qml.expval(qml.PauliX(0) @ qml.PauliY(1))
Pulse-based circuits can be executed and differentiated on the
default.qubit.jax
simulator using JAX as an interface:>>> dev = qml.device("default.qubit.jax", wires=2) >>> qnode = qml.QNode(pulse_circuit, dev, interface="jax") >>> params = (p1, p2) >>> qnode(params, time=0.5) Array(0.72153819, dtype=float64) >>> jax.grad(qnode)(params, time=0.5) (Array(-0.11324919, dtype=float64), Array([-0.64399616, 0.06326374], dtype=float64))
Check out the qml.pulse documentation page for more details!
Special unitary operation ๐
A new operation
qml.SpecialUnitary
has been added, providing access to an arbitrary unitary gate via a parametrization in the Pauli basis. (#3650) (#3651) (#3674)qml.SpecialUnitary
creates a unitary that exponentiates a linear combination of all possible Pauli words in lexicographical order โ except for the identity operator โ fornum_wires
wires, of which there are4**num_wires - 1
. As its first argument,qml.SpecialUnitary
takes a list of the4**num_wires - 1
parameters that are the coefficients of the linear combination.To see all possible Pauli words for
num_wires
wires, you can use theqml.ops.qubit.special_unitary.pauli_basis_strings
function:>>> qml.ops.qubit.special_unitary.pauli_basis_strings(1) # 4**1-1 = 3 Pauli words ['X', 'Y', 'Z'] >>> qml.ops.qubit.special_unitary.pauli_basis_strings(2) # 4**2-1 = 15 Pauli words ['IX', 'IY', 'IZ', 'XI', 'XX', 'XY', 'XZ', 'YI', 'YX', 'YY', 'YZ', 'ZI', 'ZX', 'ZY', 'ZZ']
To use
qml.SpecialUnitary
, for example, on a single qubit, we may define>>> thetas = np.array([0.2, 0.1, -0.5]) >>> U = qml.SpecialUnitary(thetas, 0) >>> qml.matrix(U) array([[ 0.8537127 -0.47537233j, 0.09507447+0.19014893j], [-0.09507447+0.19014893j, 0.8537127 +0.47537233j]])
A single non-zero entry in the parameters will create a Pauli rotation:
>>> x = 0.412 >>> theta = x * np.array([1, 0, 0]) # The first entry belongs to the Pauli word "X" >>> su = qml.SpecialUnitary(theta, wires=0) >>> rx = qml.RX(-2 * x, 0) # RX introduces a prefactor -0.5 that has to be compensated >>> qml.math.allclose(qml.matrix(su), qml.matrix(rx)) True
This operation can be differentiated with hardware-compatible methods like parameter shifts and it supports parameter broadcasting/batching, but not both at the same time. Learn more by visiting the qml.SpecialUnitary documentation.
Always differentiable ๐
The Hadamard test gradient transform is now available via
qml.gradients.hadamard_grad
. This transform is also available as a differentiation method withinQNode
s. (#3625) (#3736)qml.gradients.hadamard_grad
is a hardware-compatible transform that calculates the gradient of a quantum circuit using the Hadamard test. Note that the device requires an auxiliary wire to calculate the gradient.>>> dev = qml.device("default.qubit", wires=2) >>> @qml.qnode(dev) ... def circuit(params): ... qml.RX(params[0], wires=0) ... qml.RY(params[1], wires=0) ... qml.RX(params[2], wires=0) ... return qml.expval(qml.PauliZ(0)) >>> params = np.array([0.1, 0.2, 0.3], requires_grad=True) >>> qml.gradients.hadamard_grad(circuit)(params) (tensor(-0.3875172, requires_grad=True), tensor(-0.18884787, requires_grad=True), tensor(-0.38355704, requires_grad=True))
This transform can be registered directly as the quantum gradient transform to use during autodifferentiation:
>>> dev = qml.device("default.qubit", wires=2) >>> @qml.qnode(dev, interface="jax", diff_method="hadamard") ... def circuit(params): ... qml.RX(params[0], wires=0) ... qml.RY(params[1], wires=0) ... qml.RX(params[2], wires=0) ... return qml.expval(qml.PauliZ(0)) >>> params = jax.numpy.array([0.1, 0.2, 0.3]) >>> jax.jacobian(circuit)(params) Array([-0.3875172 , -0.18884787, -0.38355705], dtype=float32)
The gradient transform
qml.gradients.spsa_grad
is now registered as a differentiation method for QNodes. (#3440)The SPSA gradient transform can now be used implicitly by marking a QNode as differentiable with SPSA. It can be selected via
>>> dev = qml.device("default.qubit", wires=1) >>> @qml.qnode(dev, interface="jax", diff_method="spsa", h=0.05, num_directions=20) ... def circuit(x): ... qml.RX(x, 0) ... return qml.expval(qml.PauliZ(0)) >>> jax.jacobian(circuit)(jax.numpy.array(0.5)) Array(-0.4792258, dtype=float32, weak_type=True)
The argument
num_directions
determines how many directions of simultaneous perturbation are used and therefore the number of circuit evaluations, up to a prefactor. See the SPSA gradient transform documentation for details. Note: The full SPSA optimization method is already available asqml.SPSAOptimizer
.The default interface is now
auto
. There is no need to specify the interface anymore; it is automatically determined by checking your QNode parameters. (#3677) (#3752) (#3829)import jax import jax.numpy as jnp qml.enable_return() a = jnp.array(0.1) b = jnp.array(0.2) dev = qml.device("default.qubit", wires=2) @qml.qnode(dev) def circuit(a, b): qml.RY(a, wires=0) qml.RX(b, wires=1) qml.CNOT(wires=[0, 1]) return qml.expval(qml.PauliZ(0)), qml.expval(qml.PauliY(1))
>>> circuit(a, b) (Array(0.9950042, dtype=float32), Array(-0.19767681, dtype=float32)) >>> jac = jax.jacobian(circuit)(a, b) >>> jac (Array(-0.09983341, dtype=float32, weak_type=True), Array(0.01983384, dtype=float32, weak_type=True))
The JAX-JIT interface now supports higher-order gradient computation with the new return types system. (#3498)
Here is an example of using JAX-JIT to compute the Hessian of a circuit:
import pennylane as qml import jax from jax import numpy as jnp jax.config.update("jax_enable_x64", True) qml.enable_return() dev = qml.device("default.qubit", wires=2) @jax.jit @qml.qnode(dev, interface="jax-jit", diff_method="parameter-shift", max_diff=2) def circuit(a, b): qml.RY(a, wires=0) qml.RX(b, wires=1) return qml.expval(qml.PauliZ(0)), qml.expval(qml.PauliZ(1)) a, b = jnp.array(1.0), jnp.array(2.0)
>>> jax.hessian(circuit, argnums=[0, 1])(a, b) (((Array(-0.54030231, dtype=float64, weak_type=True), Array(0., dtype=float64, weak_type=True)), (Array(-1.76002563e-17, dtype=float64, weak_type=True), Array(0., dtype=float64, weak_type=True))), ((Array(0., dtype=float64, weak_type=True), Array(-1.00700085e-17, dtype=float64, weak_type=True)), (Array(0., dtype=float64, weak_type=True), Array(0.41614684, dtype=float64, weak_type=True))))
The
qchem
workflow has been modified to support both Autograd and JAX frameworks. (#3458) (#3462) (#3495)The JAX interface is automatically used when the differentiable parameters are JAX objects. Here is an example for computing the Hartree-Fock energy gradients with respect to the atomic coordinates.
import pennylane as qml from pennylane import numpy as np import jax symbols = ["H", "H"] geometry = np.array([[0.0, 0.0, 0.0], [0.0, 0.0, 1.0]]) mol = qml.qchem.Molecule(symbols, geometry) args = [jax.numpy.array(mol.coordinates)]
>>> jax.grad(qml.qchem.hf_energy(mol))(*args) Array([[ 0. , 0. , 0.3650435], [ 0. , 0. , -0.3650435]], dtype=float64)
The kernel matrix utility functions in
qml.kernels
are now autodifferentiation-compatible. In addition, they support batching, for example for quantum kernel execution with shot vectors. (#3742)This allows for the following:
dev = qml.device('default.qubit', wires=2, shots=(100, 100)) @qml.qnode(dev) def circuit(x1, x2): qml.templates.AngleEmbedding(x1, wires=dev.wires) qml.adjoint(qml.templates.AngleEmbedding)(x2, wires=dev.wires) return qml.probs(wires=dev.wires) kernel = lambda x1, x2: circuit(x1, x2)
We can then compute the kernel matrix on a set of 4 (random) feature vectors
X
but using two sets of 100 shots each via>>> X = np.random.random((4, 2)) >>> qml.kernels.square_kernel_matrix(X, kernel)[:, 0] tensor([[[1. , 0.86, 0.88, 0.92], [0.86, 1. , 0.75, 0.97], [0.88, 0.75, 1. , 0.91], [0.92, 0.97, 0.91, 1. ]], [[1. , 0.93, 0.91, 0.92], [0.93, 1. , 0.8 , 1. ], [0.91, 0.8 , 1. , 0.91], [0.92, 1. , 0.91, 1. ]]], requires_grad=True)
Note that we have extracted the first probability vector entry for each 100-shot evaluation.
Smartly decompose Hamiltonian evolution ๐ฏ
Hamiltonian evolution using
qml.evolve
orqml.exp
can now be decomposed into operations. (#3691) (#3777)If the time-evolved Hamiltonian is equivalent to another PennyLane operation, then that operation is returned as the decomposition:
>>> exp_op = qml.evolve(qml.PauliX(0) @ qml.PauliX(1)) >>> exp_op.decomposition() [IsingXX((2+0j), wires=[0, 1])]
If the Hamiltonian is a Pauli word, then the decomposition is provided as a
qml.PauliRot
operation:>>> qml.evolve(qml.PauliZ(0) @ qml.PauliX(1)).decomposition() [PauliRot((2+0j), ZX, wires=[0, 1])]
Otherwise, the Hamiltonian is a linear combination of operators and the Suzuki-Trotter decomposition is used:
>>> qml.evolve(qml.sum(qml.PauliX(0), qml.PauliY(0), qml.PauliZ(0)), num_steps=2).decomposition() [RX((1+0j), wires=[0]), RY((1+0j), wires=[0]), RZ((1+0j), wires=[0]), RX((1+0j), wires=[0]), RY((1+0j), wires=[0]), RZ((1+0j), wires=[0])]
Tools for quantum chemistry and other applications ๐ ๏ธ
A new method called
qml.qchem.givens_decomposition
has been added, which decomposes a unitary into a sequence of Givens rotation gates with phase shifts and a diagonal phase matrix. (#3573)unitary = np.array([[ 0.73678+0.27511j, -0.5095 +0.10704j, -0.06847+0.32515j], [-0.21271+0.34938j, -0.38853+0.36497j, 0.61467-0.41317j], [ 0.41356-0.20765j, -0.00651-0.66689j, 0.32839-0.48293j]]) phase_mat, ordered_rotations = qml.qchem.givens_decomposition(unitary)
>>> phase_mat tensor([-0.20604358+0.9785369j , -0.82993272+0.55786114j, 0.56230612-0.82692833j], requires_grad=True) >>> ordered_rotations [(tensor([[-0.65087861-0.63937521j, -0.40933651-0.j ], [-0.29201359-0.28685265j, 0.91238348-0.j ]], requires_grad=True), (0, 1)), (tensor([[ 0.47970366-0.33308926j, -0.8117487 -0.j ], [ 0.66677093-0.46298215j, 0.5840069 -0.j ]], requires_grad=True), (1, 2)), (tensor([[ 0.36147547+0.73779454j, -0.57008306-0.j ], [ 0.2508207 +0.51194108j, 0.82158706-0.j ]], requires_grad=True), (0, 1))]
A new template called
qml.BasisRotation
has been added, which performs a basis transformation defined by a set of fermionic ladder operators. (#3573)import pennylane as qml from pennylane import numpy as np V = np.array([[ 0.53672126+0.j , -0.1126064 -2.41479668j], [-0.1126064 +2.41479668j, 1.48694623+0.j ]]) eigen_vals, eigen_vecs = np.linalg.eigh(V) umat = eigen_vecs.T wires = range(len(umat)) def circuit(): qml.adjoint(qml.BasisRotation(wires=wires, unitary_matrix=umat)) for idx, eigenval in enumerate(eigen_vals): qml.RZ(eigenval, wires=[idx]) qml.BasisRotation(wires=wires, unitary_matrix=umat)
>>> circ_unitary = qml.matrix(circuit)() >>> np.round(circ_unitary/circ_unitary[0][0], 3) tensor([[ 1. -0.j , -0. +0.j , -0. +0.j , -0. +0.j ], [-0. +0.j , -0.516-0.596j, -0.302-0.536j, -0. +0.j ], [-0. +0.j , 0.35 +0.506j, -0.311-0.724j, -0. +0.j ], [-0. +0.j , -0. +0.j , -0. +0.j , -0.438+0.899j]], requires_grad=True)
A new function called
qml.qchem.load_basisset
has been added to extractqml.qchem
basis set data from the Basis Set Exchange library. (#3363)A new function called
qml.math.max_entropy
has been added to compute the maximum entropy of a quantum state. (#3594)A new template called
qml.TwoLocalSwapNetwork
has been added that implements a canonical 2-complete linear (2-CCL) swap network described in arXiv:1905.05118. (#3447)dev = qml.device('default.qubit', wires=5) weights = np.random.random(size=qml.templates.TwoLocalSwapNetwork.shape(len(dev.wires))) acquaintances = lambda index, wires, param: (qml.CRY(param, wires=index) if np.abs(wires[0]-wires[1]) else qml.CRZ(param, wires=index)) @qml.qnode(dev) def swap_network_circuit(): qml.templates.TwoLocalSwapNetwork(dev.wires, acquaintances, weights, fermionic=False) return qml.state()
>>> print(weights) tensor([0.20308242, 0.91906199, 0.67988804, 0.81290256, 0.08708985, 0.81860084, 0.34448344, 0.05655892, 0.61781612, 0.51829044], requires_grad=True) >>> print(qml.draw(swap_network_circuit, expansion_strategy = 'device')()) 0: โโญโโโโโโโโโโญSWAPโโโโโโโโโโโโโโโโโโญโโโโโโโโโโญSWAPโโโโโโโโโโโโโโโโโโญโโโโโโโโโโญSWAPโโค State 1: โโฐRY(0.20)โโฐSWAPโโญโโโโโโโโโโญSWAPโโฐRY(0.09)โโฐSWAPโโญโโโโโโโโโโญSWAPโโฐRY(0.62)โโฐSWAPโโค State 2: โโญโโโโโโโโโโญSWAPโโฐRY(0.68)โโฐSWAPโโญโโโโโโโโโโญSWAPโโฐRY(0.34)โโฐSWAPโโญโโโโโโโโโโญSWAPโโค State 3: โโฐRY(0.92)โโฐSWAPโโญโโโโโโโโโโญSWAPโโฐRY(0.82)โโฐSWAPโโญโโโโโโโโโโญSWAPโโฐRY(0.52)โโฐSWAPโโค State 4: โโโโโโโโโโโโโโโโโโฐRY(0.81)โโฐSWAPโโโโโโโโโโโโโโโโโโฐRY(0.06)โโฐSWAPโโโโโโโโโโโโโโโโโโค State
Improvements ๐
Pulse programming
A new function called
qml.pulse.pwc
has been added as a convenience function for defining aqml.pulse.ParametrizedHamiltonian
. This function can be used to create a callable coefficient by setting the timespan over which the function should be non-zero. The resulting callable can be passed an array of parameters and a time. (#3645)>>> timespan = (2, 4) >>> f = qml.pulse.pwc(timespan) >>> f * qml.PauliX(0) ParametrizedHamiltonian: terms=1
The
params
array will be used as bin values evenly distributed over the timespan, and the parametert
will determine which of the bins is returned.>>> f(params=[1.2, 2.3, 3.4, 4.5], t=3.9) DeviceArray(4.5, dtype=float32) >>> f(params=[1.2, 2.3, 3.4, 4.5], t=6) # zero outside the range (2, 4) DeviceArray(0., dtype=float32)
A new function called
qml.pulse.pwc_from_function
has been added as a decorator for defining aqml.pulse.ParametrizedHamiltonian
. This function can be used to decorate a function and create a piecewise constant approximation of it. (#3645)>>> @qml.pulse.pwc_from_function((2, 4), num_bins=10) ... def f1(p, t): ... return p * t
The resulting function approximates the same of
p**2 * t
on the intervalt=(2, 4)
in 10 bins, and returns zero outside the interval.# t=2 and t=2.1 are within the same bin >>> f1(3, 2), f1(3, 2.1) (DeviceArray(6., dtype=float32), DeviceArray(6., dtype=float32)) # next bin >>> f1(3, 2.2) DeviceArray(6.6666665, dtype=float32) # outside the interval t=(2, 4) >>> f1(3, 5) DeviceArray(0., dtype=float32)
Add
ParametrizedHamiltonianPytree
class, which is a pytree jax object representing a parametrized Hamiltonian, where the matrix computation is delayed to improve performance. (#3779)
Operations and batching
The function
qml.dot
has been updated to compute the dot product between a vector and a list of operators. (#3586)>>> coeffs = np.array([1.1, 2.2]) >>> ops = [qml.PauliX(0), qml.PauliY(0)] >>> qml.dot(coeffs, ops) (1.1*(PauliX(wires=[0]))) + (2.2*(PauliY(wires=[0]))) >>> qml.dot(coeffs, ops, pauli=True) 1.1 * X(0) + 2.2 * Y(0)
qml.evolve
returns the evolution of anOperator
or aParametrizedHamiltonian
. (#3617) (#3706)qml.ControlledQubitUnitary
now inherits fromqml.ops.op_math.ControlledOp
, which definesdecomposition
,expand
, andsparse_matrix
rather than raising an error. (#3450)Parameter broadcasting support has been added for the
qml.ops.op_math.Controlled
class if the base operator supports broadcasting. (#3450)The
qml.generator
function now checks if the generator is Hermitian, rather than whether it is a subclass ofObservable
. This allows it to return valid generators fromSymbolicOp
andCompositeOp
classes. (#3485)The
qml.equal
function has been extended to compareProd
andSum
operators. (#3516)qml.purity
has been added as a measurement process for purity (#3551)In-place inversion has been removed for qutrit operations in preparation for the removal of in-place inversion. (#3566)
The
qml.utils.sparse_hamiltonian
function has been moved to theeqml.Hamiltonian.sparse_matrix
method. (#3585)The
qml.pauli.PauliSentence.operation()
method has been improved to avoid instantiating anSProd
operator when the coefficient is equal to 1. (#3595)Batching is now allowed in all
SymbolicOp
operators, which includeExp
,Pow
andSProd
. (#3597)The
Sum
andProd
operations now have broadcasted operands. (#3611)The XYX single-qubit unitary decomposition has been implemented. (#3628)
All dunder methods now return
NotImplemented
, allowing the right dunder method (e.g.__radd__
) of the other class to be called. (#3631)The
qml.GellMann
operators now include their index when displayed. (#3641)qml.ops.ctrl_decomp_zyz
has been added to compute the decomposition of a controlled single-qubit operation given a single-qubit operation and the control wires. (#3681)qml.pauli.is_pauli_word
now supportsProd
andSProd
operators, and it returnsFalse
when aHamiltonian
contains more than one term. (#3692)qml.pauli.pauli_word_to_string
now supportsProd
,SProd
andHamiltonian
operators. (#3692)qml.ops.op_math.Controlled
can now decompose single qubit target operations more effectively using the ZYZ decomposition. (#3726)The
qml.qchem.Molecule
class raises an error when the molecule has an odd number of electrons or when the spin multiplicity is not 1. (#3748)
qml.qchem.basis_rotation
now accounts for spin, allowing it to perform Basis Rotation Groupings for molecular hamiltonians. (#3714) (#3774)The gradient transforms work for the new return type system with non-trivial classical jacobians. (#3776)
The
default.mixed
device has received a performance improvement for multi-qubit operations. This also allows to apply channels that act on more than seven qubits, which was not possible before. (#3584)qml.dot
now groups coefficients together. (#3691)>>> qml.dot(coeffs=[2, 2, 2], ops=[qml.PauliX(0), qml.PauliY(1), qml.PauliZ(2)]) 2*(PauliX(wires=[0]) + PauliY(wires=[1]) + PauliZ(wires=[2]))
qml.generator
now supports operators withSum
andProd
generators. (#3691)The
Sum._sort
method now takes into account the name of the operator when sorting. (#3691)A new tape transform called
qml.transforms.sign_expand
has been added. It implements the optimal decomposition of a fast-forwardable Hamiltonian that minimizes the variance of its estimator in the Single-Qubit-Measurement from arXiv:2207.09479. (#2852)
Differentiability and interfaces
The
qml.math
module now also contains a submodule for fast Fourier transforms,qml.math.fft
. (#1440)The submodule in particular provides differentiable versions of the following functions, available in all common interfaces for PennyLane
Note that the output of the derivative of these functions may differ when used with complex-valued inputs, due to different conventions on complex-valued derivatives.
Validation has been added on gradient keyword arguments when initializing a QNode โ if unexpected keyword arguments are passed, a
UserWarning
is raised. A list of the current expected gradient function keyword arguments can be accessed viaqml.gradients.SUPPORTED_GRADIENT_KWARGS
. (#3526)The
numpy
version has been constrained to<1.24
. (#3563)Support for two-qubit unitary decomposition with JAX-JIT has been added. (#3569)
qml.math.size
now supports PyTorch tensors. (#3606)Most quantum channels are now fully differentiable on all interfaces. (#3612)
qml.math.matmul
now supports PyTorch and Autograd tensors. (#3613)Add
qml.math.detach
, which detaches a tensor from its trace. This stops automatic gradient computations. (#3674)Add
typing.TensorLike
type. (#3675)qml.QuantumMonteCarlo
template is now JAX-JIT compatible when passingjax.numpy
arrays to the template. (#3734)DefaultQubitJax
now supports evolving the state vector when executingqml.pulse.ParametrizedEvolution
gates. (#3743)SProd.sparse_matrix
now supports interface-specific variables with a single element as thescalar
. (#3770)Added
argnum
argument tometric_tensor
. By passing a sequence of indices referring to trainable tape parameters, the metric tensor is only computed with respect to these parameters. This reduces the number of tapes that have to be run. (#3587)The parameter-shift derivative of variances saves a redundant evaluation of the corresponding unshifted expectation value tape, if possible (#3744)
Next generation device API
The
apply_operation
single-dispatch function is added todevices/qubit
that applies an operation to a state and returns a new state. (#3637)The
preprocess
function is added todevices/qubit
that validates, expands, and transforms a batch ofQuantumTape
objects to abstract preprocessing details away from the device. (#3708)The
create_initial_state
function is added todevices/qubit
that returns an initial state for an execution. (#3683)The
simulate
function is added todevices/qubit
that turns a single quantum tape into a measurement result. The function only supports state based measurements with either no observables or observables with diagonalizing gates. It supports simultaneous measurement of non-commuting observables. (#3700)The
ExecutionConfig
data class has been added. (#3649)The
StatePrep
class has been added as an interface that state-prep operators must implement. (#3654)qml.QubitStateVector
now implements theStatePrep
interface. (#3685)qml.BasisState
now implements theStatePrep
interface. (#3693)New Abstract Base Class for devices
Device
is added to thedevices.experimental
submodule. This interface is still in experimental mode and not integrated with the rest of pennylane. (#3602)
Other improvements
Writing Hamiltonians to a file using the
qml.data
module has been improved by employing a condensed writing format. (#3592)Lazy-loading in the
qml.data.Dataset.read()
method is more universally supported. (#3605)The
qchem.Molecule
class raises an error when the molecule has an odd number of electrons or when the spin multiplicity is not 1. (#3748)qml.draw
andqml.draw_mpl
have been updated to draw any quantum function, which allows for visualizing only part of a complete circuit/QNode. (#3760)The string representation of a Measurement Process now includes the
_eigvals
property if it is set. (#3820)
Breaking changes ๐
The argument
mode
in execution has been replaced by the booleangrad_on_execution
in the new execution pipeline. (#3723)qml.VQECost
has been removed. (#3735)The default interface is now
auto
. (#3677) (#3752) (#3829)The interface is determined during the QNode call instead of the initialization. It means that the
gradient_fn
andgradient_kwargs
are only defined on the QNode at the beginning of the call. Moreover, without specifying the interface it is not possible to guarantee that the device will not be changed during the call if you are using backprop (such asdefault.qubit
changing todefault.qubit.jax
) whereas before it was happening at initialization.The tape method
get_operation
can also now return the operation index in the tape, and it can be activated by setting thereturn_op_index
toTrue
:get_operation(idx, return_op_index=True)
. It will become the default in version0.30
. (#3667)Operation.inv()
and theOperation.inverse
setter have been removed. Please useqml.adjoint
orqml.pow
instead. (#3618)For example, instead of
>>> qml.PauliX(0).inv()
use
>>> qml.adjoint(qml.PauliX(0))
The
Operation.inverse
property has been removed completely. (#3725)The target wires of
qml.ControlledQubitUnitary
are no longer available viaop.hyperparameters["u_wires"]
. Instead, they can be accesses viaop.base.wires
orop.target_wires
. (#3450)The tape constructed by a
QNode
is no longer queued to surrounding contexts. (#3509)Nested operators like
Tensor
,Hamiltonian
, andAdjoint
now remove their owned operators from the queue instead of updating their metadata to have an"owner"
. (#3282)qml.qchem.scf
,qml.RandomLayers.compute_decomposition
, andqml.Wires.select_random
now use local random number generators instead of global random number generators. This may lead to slightly different random numbers and an independence of the results from the global random number generation state. Please provide a seed to each individual function instead if you want controllable results. (#3624)qml.transforms.measurement_grouping
has been removed. Users should useqml.transforms.hamiltonian_expand
instead. (#3701)op.simplify()
for operators which are linear combinations of Pauli words will use a builtin Pauli representation to more efficiently compute the simplification of the operator. (#3481)All
Operator
โs input parameters that are lists are cast into vanilla numpy arrays. (#3659)QubitDevice.expval
no longer permutes an observableโs wire order before passing it toQubitDevice.probability
. The associated downstream changes fordefault.qubit
have been made, but this may still affect expectations for other devices that inherit fromQubitDevice
and overrideprobability
(or any other helper functions that take a wire order such asmarginal_prob
,estimate_probability
oranalytic_probability
). (#3753)
Deprecations ๐
qml.utils.sparse_hamiltonian
function has been deprecated, and usage will now raise a warning. Instead, one should use theqml.Hamiltonian.sparse_matrix
method. (#3585)qml.op_sum
has been deprecated. Users should useqml.sum
instead. (#3686)The use of
Evolution
directly has been deprecated. Users should useqml.evolve
instead. This new function changes the sign of the given parameter. (#3706)Use of
qml.dot
with aQNodeCollection
has been deprecated. (#3586)
Documentation ๐
Revise note on GPU support in the circuit introduction. (#3836)
Make warning about vanilla version of NumPy for differentiation more prominent. (#3838)
The documentation for
qml.operation
has been improved. (#3664)The code example in
qml.SparseHamiltonian
has been updated with the correct wire range. (#3643)A hyperlink has been added in the text for a URL in the
qml.qchem.mol_data
docstring. (#3644)A typo was corrected in the documentation for
qml.math.vn_entropy
. (#3740)
Bug fixes ๐
Fixed a bug where measuring
qml.probs
in the computational basis with non-commuting measurements returned incorrect results. Now an error is raised. (#3811)Fixed a bug where measuring
qml.probs
in the computational basis with non-commuting measurements returned incorrect results. Now an error is raised. (#3811)Fixed a bug in the drawer where nested controlled operations would output the label of the operation being controlled, rather than the control values. (#3745)
Fixed a bug in
qml.transforms.metric_tensor
where prefactors of operation generators were taken into account multiple times, leading to wrong outputs for non-standard operations. (#3579)Local random number generators are now used where possible to avoid mutating the global random state. (#3624)
The
networkx
version change being broken has been fixed by selectively skipping aqcut
TensorFlow-JIT test. (#3609) (#3619)Fixed the wires for the
Y
decomposition in the ZX calculus transform. (#3598)qml.pauli.PauliWord
is now pickle-able. (#3588)Child classes of
QuantumScript
now return their own type when usingSomeChildClass.from_queue
. (#3501)A typo has been fixed in the calculation and error messages in
operation.py
(#3536)qml.data.Dataset.write()
now ensures that any lazy-loaded values are loaded before they are written to a file. (#3605)Tensor._batch_size
is now set toNone
during initialization, copying andmap_wires
. (#3642) (#3661)Tensor.has_matrix
is now set toTrue
. (#3647)Fixed typo in the example of
qml.IsingZZ
gate decomposition. (#3676)Fixed a bug that made tapes/qnodes using
qml.Snapshot
incompatible withqml.drawer.tape_mpl
. (#3704)Tensor._pauli_rep
is set toNone
during initialization andTensor.data
has been added to its setter. (#3722)qml.math.ndim
has been redirected tojnp.ndim
when using it on ajax
tensor. (#3730)Implementations of
marginal_prob
(and subsequently,qml.probs
) now return probabilities with the expected wire order. (#3753)This bug affected most probabilistic measurement processes on devices that inherit from
QubitDevice
when the measured wires are out of order with respect to the device wires and 3 or more wires are measured. The assumption was that marginal probabilities would be computed with the deviceโs state and wire order, then re-ordered according to the measurement process wire order. Instead, the re-ordering went in the inverse direction (that is, from measurement process wire order to device wire order). This is now fixed. Note that this only occurred for 3 or more measured wires because this mapping is identical otherwise. More details and discussion of this bug can be found in the original bug report.Empty iterables can no longer be returned from QNodes. (#3769)
The keyword arguments for
qml.equal
now are used when comparing the observables of a Measurement Process. The eigvals of measurements are only requested if both observables areNone
, saving computational effort. (#3820)Only converts input to
qml.Hermitian
to a numpy array if the input is a list. (#3820)
Contributors โ
This release contains contributions from (in alphabetical order):
Gian-Luca Anselmetti, Guillermo Alonso-Linaje, Juan Miguel Arrazola, Ikko Ashimine, Utkarsh Azad, Miriam Beddig, Cristian Boghiu, Thomas Bromley, Astral Cai, Isaac De Vlugt, Olivia Di Matteo, Lillian M. A. Frederiksen, Soran Jahangiri, Korbinian Kottmann, Christina Lee, Albert Mitjans Coma, Romain Moyard, Mudit Pandey, Borja Requena, Matthew Silverman, Jay Soni, Antal Szรกva, Frederik Wilde, David Wierichs, Moritz Willmann.
- orphan
Release 0.28.0ยถ
New features since last release
Custom measurement processes ๐
Custom measurements can now be facilitated with the addition of the
qml.measurements
module. (#3286) (#3343) (#3288) (#3312) (#3287) (#3292) (#3287) (#3326) (#3327) (#3388) (#3439) (#3466)Within
qml.measurements
are new subclasses that allow for the possibility to create custom measurements:SampleMeasurement
: represents a sample-based measurementStateMeasurement
: represents a state-based measurementMeasurementTransform
: represents a measurement process that requires the application of a batch transform
Creating a custom measurement involves making a class that inherits from one of the classes above. An example is given below. Here, the measurement computes the number of samples obtained of a given state:
from pennylane.measurements import SampleMeasurement class CountState(SampleMeasurement): def __init__(self, state: str): self.state = state # string identifying the state, e.g. "0101" wires = list(range(len(state))) super().__init__(wires=wires) def process_samples(self, samples, wire_order, shot_range, bin_size): counts_mp = qml.counts(wires=self._wires) counts = counts_mp.process_samples(samples, wire_order, shot_range, bin_size) return counts.get(self.state, 0) def __copy__(self): return CountState(state=self.state)
We can now execute the new measurement in a QNode as follows.
dev = qml.device("default.qubit", wires=1, shots=10000) @qml.qnode(dev) def circuit(x): qml.RX(x, wires=0) return CountState(state="1")
>>> circuit(1.23) tensor(3303., requires_grad=True)
Differentiability is also supported for this new measurement process:
>>> x = qml.numpy.array(1.23, requires_grad=True) >>> qml.grad(circuit)(x) 4715.000000000001
For more information about these new features, see the documentation for ``qml.measurements` <https://docs.pennylane.ai/en/stable/code/qml_measurements.html>`_.
ZX Calculus ๐งฎ
QNodes can now be converted into ZX diagrams via the PyZX framework. (#3446)
ZX diagrams are the medium for which we can envision a quantum circuit as a graph in the ZX-calculus language, showing properties of quantum protocols in a visually compact and logically complete fashion.
QNodes decorated with
@qml.transforms.to_zx
will return a PyZX graph that represents the computation in the ZX-calculus language.dev = qml.device("default.qubit", wires=2) @qml.transforms.to_zx @qml.qnode(device=dev) def circuit(p): qml.RZ(p[0], wires=1), qml.RZ(p[1], wires=1), qml.RX(p[2], wires=0), qml.PauliZ(wires=0), qml.RZ(p[3], wires=1), qml.PauliX(wires=1), qml.CNOT(wires=[0, 1]), qml.CNOT(wires=[1, 0]), qml.SWAP(wires=[0, 1]), return qml.expval(qml.PauliZ(0) @ qml.PauliZ(1))
>>> params = [5 / 4 * np.pi, 3 / 4 * np.pi, 0.1, 0.3] >>> circuit(params) Graph(20 vertices, 23 edges)
Information about PyZX graphs can be found in the PyZX Graphs API.
QChem databases and basis sets โ๏ธ
The symbols and geometry of a compound from the PubChem database can now be accessed via
qchem.mol_data()
. (#3289) (#3378)>>> import pennylane as qml >>> from pennylane.qchem import mol_data >>> mol_data("BeH2") (['Be', 'H', 'H'], tensor([[ 4.79404621, 0.29290755, 0. ], [ 3.77945225, -0.29290755, 0. ], [ 5.80882913, -0.29290755, 0. ]], requires_grad=True)) >>> mol_data(223, "CID") (['N', 'H', 'H', 'H', 'H'], tensor([[ 0. , 0. , 0. ], [ 1.82264085, 0.52836742, 0.40402345], [ 0.01417295, -1.67429735, -0.98038991], [-0.98927163, -0.22714508, 1.65369933], [-0.84773114, 1.373075 , -1.07733286]], requires_grad=True))
Perform quantum chemistry calculations with two new basis sets:
6-311g
andCC-PVDZ
. (#3279)>>> symbols = ["H", "He"] >>> geometry = np.array([[1.0, 0.0, 0.0], [0.0, 0.0, 0.0]], requires_grad=False) >>> charge = 1 >>> basis_names = ["6-311G", "CC-PVDZ"] >>> for basis_name in basis_names: ... mol = qml.qchem.Molecule(symbols, geometry, charge=charge, basis_name=basis_name) ... print(qml.qchem.hf_energy(mol)()) [-2.84429531] [-2.84061284]
A bunch of new operators ๐
The controlled CZ gate and controlled Hadamard gate are now available via
qml.CCZ
andqml.CH
, respectively. (#3408)>>> ccz = qml.CCZ(wires=[0, 1, 2]) >>> qml.matrix(ccz) [[ 1 0 0 0 0 0 0 0] [ 0 1 0 0 0 0 0 0] [ 0 0 1 0 0 0 0 0] [ 0 0 0 1 0 0 0 0] [ 0 0 0 0 1 0 0 0] [ 0 0 0 0 0 1 0 0] [ 0 0 0 0 0 0 1 0] [ 0 0 0 0 0 0 0 -1]] >>> ch = qml.CH(wires=[0, 1]) >>> qml.matrix(ch) [[ 1. 0. 0. 0. ] [ 0. 1. 0. 0. ] [ 0. 0. 0.70710678 0.70710678] [ 0. 0. 0.70710678 -0.70710678]]
Three new parametric operators,
qml.CPhaseShift00
,qml.CPhaseShift01
, andqml.CPhaseShift10
, are now available. Each of these operators performs a phase shift akin toqml.ControlledPhaseShift
but on different positions of the state vector. (#2715)>>> dev = qml.device("default.qubit", wires=2) >>> @qml.qnode(dev) >>> def circuit(): ... qml.PauliX(wires=1) ... qml.CPhaseShift01(phi=1.23, wires=[0,1]) ... return qml.state() ... >>>