Deprecations¶

All PennyLane deprecations will raise a qml.exceptions.PennyLaneDeprecationWarning. Pending and completed deprecations are listed below.

Pending deprecations¶

Setting shots on a device through the shots keyword argument is deprecated. Instead, please specify shots using the shots keyword argument of QNode, or use the pennylane.set_shots() transform on the QNode.
```
dev = qml.device("default.qubit", wires=2)

@qml.qnode(dev, shots=1000)
def circuit(x):
    qml.RX(x, wires=0)
    return qml.expval(qml.Z(0))

circuit_analytic = qml.set_shots(circuit, None)
```
- Deprecated in v0.43
- Will be removed in a future version
Maintenance support for the tensorflow interface has been deprecated and will be dropped in PennyLane v0.44. Future versions of PennyLane are not guaranteed to work with TensorFlow. Instead, we recommend using the jax or torch interface for machine learning applications to benefit from enhanced support and features.
- Deprecated in v0.43
- Will be removed in v0.44
pennylane.devices.DefaultExecutionConfig is deprecated and will be removed in v0.44. Instead, use qml.devices.ExecutionConfig() to create a default execution configuration.
- Deprecated in v0.43
- Will be removed in v0.44
Specifying the work_wire_type argument in qml.ctrl and other controlled operators as "clean" or "dirty" is deprecated. Use "zeroed" to indicate that the work wires are initially in the \(|0\rangle\) state, and "borrowed" to indicate that the work wires can be in any arbitrary state. In both cases, the work wires are restored to their original state upon completing the decomposition.
- Deprecated in v0.43
- Will be removed in v0.44

Providing num_steps to pennylane.evolve(), pennylane.exp(), pennylane.ops.Evolution, and pennylane.ops.Exp is deprecated and will be removed in a future release. Instead, use TrotterProduct for approximate methods, providing the n parameter to perform the Suzuki-Trotter product approximation of a Hamiltonian with the specified number of Trotter steps.

As a concrete example, consider the following case:

coeffs = [0.5, -0.6]
ops = [qml.X(0), qml.X(0) @ qml.Y(1)]
H_flat = qml.dot(coeffs, ops)

Instead of computing the Suzuki-Trotter product approximation as:

>>> qml.evolve(H_flat, num_steps=2).decomposition()
[RX(0.5, wires=[0]),
PauliRot(-0.6, XY, wires=[0, 1]),
RX(0.5, wires=[0]),
PauliRot(-0.6, XY, wires=[0, 1])]

The same result can be obtained using TrotterProduct as follows:

>>> decomp_ops = qml.adjoint(qml.TrotterProduct(H_flat, time=1.0, n=2)).decomposition()
>>> [simp_op for op in decomp_ops for simp_op in map(qml.simplify, op.decomposition())]
[RX(0.5, wires=[0]),
PauliRot(-0.6, XY, wires=[0, 1]),
RX(0.5, wires=[0]),
PauliRot(-0.6, XY, wires=[0, 1])]

Deprecated in v0.43
Will be removed in a future version

MeasurementProcess.expand is deprecated. The relevant method can be replaced with qml.tape.QuantumScript(mp.obs.diagonalizing_gates(), [type(mp)(eigvals=mp.obs.eigvals(), wires=mp.obs.wires)]).
- Deprecated in v0.43
- Will be removed in v0.44
Specifying shots as a keyword argument when executing a QNode is deprecated and will be removed in v0.44. Instead, please set shots on QNode initialization, or use the set_shots() transform to set the number of shots.
- Deprecated in v0.43
- Will be removed in v0.44
The QuantumScript.shape and QuantumScript.numeric_type properties are deprecated and will be removed in version v0.44. Instead, the corresponding .shape or .numeric_type of the MeasurementProcess class should be used.
- Deprecated in v0.43
- Will be removed in v0.44
Some unnecessary methods of the qml.CircuitGraph class are deprecated and will be removed in version v0.44:
- print_contents in favor of print(obj)
- observables_in_order in favor of observables
- operations_in_order in favor of operations
- ancestors_in_order(obj) in favor of ancestors(obj, sort=True)
- descendants_in_order(obj) in favor of descendants(obj, sort=True)
- Deprecated in v0.43
- Will be removed in v0.44
The QuantumScript.to_openqasm method is deprecated and will be removed in version v0.44. Instead, the qml.to_openqasm function should be used.
- Deprecated in v0.43
- Will be removed in v0.44
qml.qnn.cost.SquaredErrorLoss is deprecated and will be removed in version v0.44. Instead, this hybrid workflow can be accomplished with a function like loss = lambda *args: (circuit(*args) - target)**2.
- Deprecated in v0.43
- Will be removed in v0.44
Access to add_noise, insert and noise mitigation transforms from the pennylane.transforms module is deprecated. Instead, these functions should be imported from the pennylane.noise module.
- Deprecated in v0.43
- Will be removed in v0.44
Passing the value None to the level argument in the pennylane.workflow.get_transform_program(), pennylane.workflow.construct_batch() , pennylane.draw(), pennylane.draw_mpl(), and pennylane.specs() transforms is deprecated and will be removed in v0.44. Please use level='device' instead to apply the transform at the device level.
- Deprecated in v0.43
- Will be removed in v0.44
The qml.QNode.add_transform method is deprecated and will be removed in v0.44. Instead, please use QNode.transform_program.push_back(transform_container=transform_container).
- Deprecated in v0.43
- Will be removed in v0.44

Completed removal of legacy operator arithmetic¶

In PennyLane v0.40, the legacy operator arithmetic system has been removed, and is fully replaced by the new operator arithmetic functionality that was introduced in v0.36. Check out the Updated operators page for details on how to port your legacy code to the new system. The following functionality has been removed:

In PennyLane v0.40, legacy operator arithmetic has been removed. This includes pennylane.operation.enable_new_opmath(), pennylane.operation.disable_new_opmath(), pennylane.ops.Hamiltonian, and pennylane.operation.Tensor. Note that qml.Hamiltonian will continue to dispatch to pennylane.ops.LinearCombination.
- Deprecated in v0.39
- Removed in v0.40
pennylane.pauli.PauliSentence.hamiltonian() and pennylane.pauli.PauliWord.hamiltonian() have been removed. Instead, please use pennylane.pauli.PauliSentence.operation() and pennylane.pauli.PauliWord.operation() respectively.
- Deprecated in v0.39
- Removed in v0.40
pennylane.pauli.simplify() has been removed. Instead, please use pennylane.simplify() or pennylane.operation.Operator.simplify().
- Deprecated in v0.39
- Removed in v0.40

Completed deprecation cycles¶

The boolean functions provided by pennylane.operation have been removed. See below for an example of alternative code to use. These include not_tape, has_gen, has_grad_method, has_multipar, has_nopar, has_unitary_gen, is_measurement, defines_diagonalizing_gates, and gen_is_multi_term_hamiltonian.
- Deprecated in v0.42
- Removed in v0.43

from pennylane.operation import TermsUndefinedError, Operator

def not_tape(obj):
    return not isinstance(obj, qml.tape.QuantumScript)

def has_gen(obj):
    return obj.has_generator

def has_grad_method(obj):
    return obj.grad_method is not None

def has_multipar(obj):
    return obj.num_params > 1

def has_nopar(obj):
    return obj.num_params == 0

def has_unitary_gen(obj):
    return obj in qml.ops.qubit.attributes.has_unitary_generator

def is_measurement(obj):
    return isinstance(obj, qml.measurements.MeasurementProcess)

def defines_diagonalizing_gates(obj):
    return obj.has_diagonalizing_gates

def gen_is_multi_term_hamiltonian(obj):
    if not isinstance(obj, Operator) or not obj.has_generator:
        return False
    try:
        generator = obj.generator()
        _, ops = generator.terms()
        return len(ops) > 1
    except TermsUndefinedError:
        return False

lie_closure, structure_constants, and center can no longer be accessed via qml.pauli. Top level import and usage is advised. They now live in the liealg module.
```
import pennylane.liealg
from pennylane.liealg import lie_closure, structure_constants, center
```
- Deprecated in v0.40
- Removed in v0.43
qml.operation.Observable has been removed. To indicate that an operator is an observable, operator developers should manually set is_hermitian = True and update the queue function to stop it from being processed into the circuit.
```
class MyObs(Operator):
    is_hermitian = True

    def queue(self, context=qml.QueuingManager):
        return self
```
To check if an operator is likely to be hermitian, the op.is_hermitian property can be checked.

Instead of Observable.compare, qml.equal and op1 == op2 should be used to compare instances.
- Deprecated in v0.42
- Removed in v0.43
qml.operation.WiresEnum, qml.operation.AllWires, and qml.operation.AnyWires have been removed. If an operation can act on any number of wires, Operator.num_wires = None should be used instead. This is the default, and does not need to be overridden unless the operator developer wants to validate that the correct number of wires is passed.
- Deprecated in v0.42
- Removed in v0.43
The qml.QNode.get_gradient_fn method has been removed. Instead, use get_best_diff_method() to obtain the differentiation method.
- Deprecated in v0.42
- Removed in v0.43
Top-level access to DeviceError, PennyLaneDeprecationWarning, QuantumFunctionError and ExperimentalWarning is now removed in v0.43. Please import these objects from the new pennylane.exceptions module.
- Deprecated in v0.42
- Removed in v0.43
Specifying gradient keyword arguments as any additional keyword argument to the qnode is now removed in v0.42. The gradient keyword arguments should be passed to the new keyword argument gradient_kwargs via an explicit dictionary, like gradient_kwargs={"h": 1e-4}.
- Deprecated in v0.41
- Removed in v0.42
The return_type property of MeasurementProcess has been removed. If observable type checking is needed, please use isinstance instead.
- Deprecated in v0.41
- Removed in v0.42
The KerasLayer class in qml.qnn.keras has been removed because Keras 2 is no longer actively maintained. Please consider using a different machine learning framework, like PyTorch or JAX.
- Deprecated in v0.41
- Removed in v0.42
The qml.gradients.hamiltonian_grad function has been removed because this gradient recipe is no longer required with the new operator arithmetic system.
- Deprecated in v0.41
- Removed in v0.42
Accessing terms of a tensor product (e.g., op = X(0) @ X(1)) via op.obs has been removed. A user should use op.operands instead.
- Deprecated in v0.36
- Removed in v0.42
The mcm_config keyword argument to qml.execute has been removed. Instead, use the mcm_method and postselect_mode arguments.
- Deprecated in v0.41
- Removed in v0.42
The inner_transform and config keyword arguments in qml.execute have been removed. If more detailed control over the execution is required, use qml.workflow.run with these arguments instead.
- Deprecated in v0.41
- Removed in v0.42
op.ops and op.coeffs for Sum and Prod have been removed. Instead, please use terms().
- Deprecated in v0.35
- Removed in v0.42
Specifying pipeline=None with qml.compile has been removed. A sequence of transforms should now always be specified.
- Deprecated in v0.41
- Removed in v0.42
The control_wires argument in the qml.ControlledQubitUnitary class has been removed. Instead, please use the wires argument.
- Deprecated in v0.41
- Removed in v0.42
The ControlledQubitUnitary no longer accepts QubitUnitary objects as arguments as its base. Instead, use qml.ctrl to construct a controlled QubitUnitary.
- Deprecated in v0.41
- Removed in v0.42
MultiControlledX no longer accepts strings as control values.
- Deprecated in v0.36
- Removed in v0.41
The input argument control_wires of MultiControlledX has been removed.
- Deprecated in v0.22
- Removed in v0.41
The decomp_depth argument in set_decomposition() has been removed.
- Deprecated in v0.40
- Removed in v0.41
The max_expansion argument in decompose() has been removed.
- Deprecated in v0.40
- Removed in v0.41
The tape and qtape properties of QNode have been removed. Instead, use the qml.workflow.construct_tape function.
- Deprecated in v0.40
- Removed in v0.41
The gradient_fn keyword argument to qml.execute has been removed. Instead, it has been replaced with diff_method.
- Deprecated in v0.40
- Removed in v0.41
The QNode.get_best_method and QNode.best_method_str methods have been removed. Instead, use the qml.workflow.get_best_diff_method function.
- Deprecated in v0.40
- Removed in v0.41
The output_dim property of qml.tape.QuantumScript has been removed. Instead, use method shape of QuantumScript or MeasurementProcess to get the same information.
- Deprecated in v0.40
- Removed in v0.41
The qml.qsvt_legacy function has been removed. Instead, use qml.qsvt. The new functionality takes an input polynomial instead of angles.
- Deprecated in v0.40
- Removed in v0.41
The qml.qinfo module has been removed. Please see the respective functions in the qml.math and qml.measurements modules instead.
- Deprecated in v0.39
- Removed in v0.40
Top level access to Device, QubitDevice, and QutritDevice have been removed. Instead, they are available as qml.devices.LegacyDevice, qml.devices.QubitDevice, and qml.devices.QutritDevice respectively.
- Deprecated in v0.39
- Removed in v0.40
The BasisStatePreparation template has been removed. Instead, use BasisState.
- Deprecated in v0.39
- Removed in v0.40
The qml.QubitStateVector template has been removed. Instead, use StatePrep.
- Deprecated in v0.39
- Removed in v0.40
qml.broadcast has been removed. Users should use for loops instead.
- Deprecated in v0.39
- Removed in v0.40
The max_expansion argument for clifford_t_decomposition() has been removed.
- Deprecated in v0.39
- Removed in v0.40
The 'ancilla' argument for iterative_qpe() has been removed. Instead, use the 'aux_wire' argument.
- Deprecated in v0.39
- Removed in v0.40
The expand_depth argument for compile() has been removed.
- Deprecated in v0.39
- Removed in v0.40
The qml.workflow.set_shots helper function has been removed. We no longer interact with the legacy device interface in our code. Instead, shots should be specified on the tape, and the device should use these shots.
- Deprecated in v0.38
- Removed in v0.40
QNode.gradient_fn is removed. Please use QNode.diff_method instead. QNode.get_gradient_fn can also be used to process the diff method.
- Deprecated in v0.39
- Removed in v0.40
The qml.shadows.shadow_expval transform has been removed. Instead, please use the qml.shadow_expval measurement process.
- Deprecated in v0.39
- Removed in v0.40
PennyLane Lightning and Catalyst will no longer support manylinux2014 (GLIBC 2.17) compatibile Linux operating systems, and will be migrated to manylinux_2_28 (GLIBC 2.28). See pypa/manylinux for additional details.
- Last supported version of manylinux2014 with v0.36
- Fully migrated to manylinux_2_28 with v0.37
The simplify argument in qml.Hamiltonian and qml.ops.LinearCombination has been removed. Instead, qml.simplify() can be called on the constructed operator.
- Deprecated in v0.37
- Removed in v0.39
The decomp_depth argument in qml.device is removed.
- Deprecated in v0.38
- Removed in v0.39
The functions qml.qinfo.classical_fisher and qml.qinfo.quantum_fisher have been removed and migrated to the qml.gradients module. Therefore, qml.gradients.classical_fisher and qml.gradients.quantum_fisher should be used instead.
- Deprecated in v0.38
- Removed in v0.39
All of the legacy devices (any with the name default.qubit.{autograd,torch,tf,jax,legacy}) are removed. Use default.qubit instead, as it supports backpropagation for the many backends the legacy devices support.
- Deprecated in v0.38
- Removed in v0.39
The logic for internally switching a device for a different backpropagation compatible device is removed, as it was in place for removed default.qubit.legacy.
- Deprecated in v0.38
- Removed in v0.39
Operator.expand is now removed. Use qml.tape.QuantumScript(op.decomposition()) instead.
- Deprecated in v0.38
- Removed in v0.39
The expansion_strategy attribute of qml.QNode is removed. Users should make use of qml.workflow.construct_batch, should they require fine control over the output tape(s).
- Deprecated in v0.38
- Removed in v0.39
The expansion_strategy argument in qml.specs, qml.draw, and qml.draw_mpl is removed. Instead, use the level argument which provides a superset of options.
- Deprecated in v0.38
- Removed in v0.39
The max_expansion argument in qml.QNode is removed.
- Deprecated in v0.38
- Removed in v0.39
The expand_fn argument in qml.execute is removed. Instead, please create a qml.transforms.core.TransformProgram with the desired preprocessing and pass it to the transform_program argument of qml.execute.
- Deprecated in v0.38
- Removed in v0.39
The max_expansion argument in qml.execute is removed. Instead, please use qml.devices.preprocess.decompose with the desired expansion level, add it to a TransformProgram, and pass it to the transform_program argument of qml.execute.
- Deprecated in v0.38
- Removed in v0.39
The override_shots argument in qml.execute is removed. Instead, please add the shots to the QuantumTapes to be executed.
- Deprecated in v0.38
- Removed in v0.39
The device_batch_transform argument in qml.execute is removed. Instead, please create a qml.transforms.core.TransformProgram with the desired preprocessing and pass it to the transform_program argument of qml.execute.
- Deprecated in v0.38
- Removed in v0.39
The functions qml.transforms.sum_expand and qml.transforms.hamiltonian_expand are removed. Instead, qml.transforms.split_non_commuting can be used for equivalent behaviour.
- Deprecated in v0.38
- Removed in v0.39
queue_idx attribute has been removed from the Operator, CompositeOp, and SymboliOp classes. Instead, the index is now stored as the label of the CircuitGraph.graph nodes.
- Deprecated in v0.38
- Removed in v0.38
qml.from_qasm no longer removes measurements from the QASM code. Use measurements=[] to remove measurements from the original circuit.
- Deprecated in v0.37
- Default behaviour changed in v0.38
qml.transforms.map_batch_transform has been removed, since transforms can be applied directly to a batch of tapes. See transform() for more information.
- Deprecated in v0.37
- Removed in v0.38
qml.from_qasm_file has been removed. Instead, the user can open the file and then load its content using qml.from_qasm.
```
>>> with open("test.qasm", "r") as f:
...     circuit = qml.from_qasm(f.read())
```
- Deprecated in v0.36
- Removed in v0.37
The qml.load function is a general-purpose way to convert circuits into PennyLane from other libraries. It has been removed in favour of the more specific functions from_qiskit, from_qasm, etc.
- Deprecated in v0.36
- Removed in v0.37
single_tape_transform, batch_transform, qfunc_transform, op_transform, gradient_transform and hessian_transform are deprecated. Instead switch to using the new qml.transform function. Please refer to the transform docs to see how this can be done.
- Deprecated in v0.34
- Removed in v0.36
PauliWord and PauliSentence no longer use * for matrix and tensor products, but instead use @ to conform with the PennyLane convention.
- Deprecated in v0.35
- Removed in v0.36
The private functions _pauli_mult, _binary_matrix and _get_pauli_map from the pauli module have been removed, as they are no longer used anywhere and the same functionality can be achieved using newer features in the pauli module.
- Deprecated in v0.35
- Removed in v0.36
Calling qml.matrix without providing a wire_order on objects where the wire order could be ambiguous now raises an error. This includes tapes with multiple wires, QNodes with a device that does not provide wires, or quantum functions.
- Deprecated in v0.35
- Raises an error in v0.36
qml.pauli.pauli_mult and qml.pauli.pauli_mult_with_phase are now removed. Instead, you should use qml.simplify(qml.prod(pauli_1, pauli_2)) to get the reduced operator.
```
>>> 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]))
```
- Deprecated in v0.35
- Removed in v0.36
MeasurementProcess.name and MeasurementProcess.data have been removed, as they contain dummy values that are no longer needed.
- Deprecated in v0.35
- Removed in v0.36
The contents of qml.interfaces is moved inside qml.workflow.
- Contents moved in v0.35
- Old import path removed in v0.36
The method Operator.validate_subspace(subspace), only employed under a specific set of qutrit operators, has been relocated to the qml.ops.qutrit.parametric_ops module and has been removed from the Operator class.
- Deprecated in v0.35
- Removed in v0.36
qml.transforms.one_qubit_decomposition and qml.transforms.two_qubit_decomposition are removed. Instead, you should use qml.ops.one_qubit_decomposition and qml.ops.two_qubit_decomposition.
- Deprecated in v0.34
- Removed in v0.35

Passing additional arguments to a transform that decorates a QNode should now be done through use of functools.partial. For example, the metric_tensor() transform has an optional approx argument which should now be set using:

from functools import partial

@partial(qml.metric_tensor, approx="block-diag")
@qml.qnode(dev)
def circuit(weights):
    ...

The previously-recommended approach is now removed:

@qml.metric_tensor(approx="block-diag")
@qml.qnode(dev)
def circuit(weights):
    ...

Alternatively, consider calling the transform directly:

@qml.qnode(dev)
def circuit(weights):
    ...

transformed_circuit = qml.metric_tensor(circuit, approx="block-diag")

Deprecated in v0.33
Removed in v0.35

Observable.return_type has been removed. Instead, you should inspect the type of the surrounding measurement process.
- Deprecated in v0.34
- Removed in v0.35
ClassicalShadow.entropy() no longer needs an atol keyword as a better method to estimate entropies from approximate density matrix reconstructions (with potentially negative eigenvalues) has been implemented.
- Deprecated in v0.34
- Removed in v0.35

QuantumScript.is_sampled and QuantumScript.all_sampled have been removed. Users should now validate these properties manually.

from pennylane.measurements import *
sample_types = (SampleMP, CountsMP, ClassicalShadowMP, ShadowExpvalMP)
is_sample_type = [isinstance(m, sample_types) for m in tape.measurements]
is_sampled = any(is_sample_type)
all_sampled = all(is_sample_type)

Deprecated in v0.34
Removed in v0.35

qml.ExpvalCost has been removed. Users should use qml.expval() instead.

@qml.qnode(dev)
def cost_function(params):
    some_qfunc(params)
    return qml.expval(Hamiltonian)

Deprecated in v0.24
Removed in v0.35

Specifying control_values passed to qml.ctrl as a string is no longer supported.
- Deprecated in v0.25
- Removed in v0.34
qml.gradients.pulse_generator has become qml.gradients.pulse_odegen to adhere to paper naming conventions.
- Deprecated in v0.33
- Removed in v0.34
The prep keyword argument in QuantumScript has been removed. StatePrepBase operations should be placed at the beginning of the ops list instead.
- Deprecated in v0.33
- Removed in v0.34
The public methods of DefaultQubit are pending changes to follow the new device API.

We will be switching to the new device interface in a coming release. In this new interface, simulation implementation details will be abstracted away from the device class itself and provided by composition, rather than inheritance. Therefore, some public and private methods from DefaultQubit will no longer exist, though its behaviour in a workflow will remain the same.

If you directly interact with device methods, please consult pennylane.devices.Device and pennylane.devices.DefaultQubit for more information on what the new interface will look like and be prepared to make updates in a coming release. If you have any feedback on these changes, please create an issue or post in our discussion forum.
- Deprecated in v0.31
- Changed in v0.33
The behaviour of Operator.__eq__ and Operator.__hash__ has been updated. Their documentation has been updated to reflect the incoming changes.

The changes to operator equality allow users to use operator equality the same way as with qml.equal. With the changes to hashing, unique operators that are equal now have the same hash. These changes now allow behaviour such as the following:
```
>>> qml.RX(0.1, wires=0) == qml.RX(0.1, wires=0)
True
>>> {qml.PauliZ(0), qml.PauliZ(0)}
{PauliZ(wires=[0])}
```
Meanwhile, the previous behaviour is shown below:
```
>>> qml.RX(0.1, wires=0) == qml.RX(0.1, wires=0)
False
>>> {qml.PauliZ(0), qml.PauliZ(0)}
{PauliZ(wires=[0]), PauliZ(wires=[0])}
```
- Added in v0.32
- Behaviour changed in v0.33
qml.qchem.jordan_wigner had been removed. Use qml.jordan_wigner instead. List input to define the fermionic operator is no longer accepted; the fermionic operators qml.FermiA, qml.FermiC, qml.FermiWord and qml.FermiSentence should be used instead. See the pennylane.fermi module documentation and the Fermionic Operator tutorial for more details.
- Deprecated in v0.32
- Removed in v0.33
The tuple input type in qubit_observable has been removed. Please use a fermionic operator object. The tuple return type in fermionic_hamiltonian and fermionic_observable has been removed and these functions will return a fermionic operator by default.
- Deprecated in v0.32
- Removed in v0.33
The sampler_seed argument of qml.gradients.spsa_grad has been removed. Instead, the sampler_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 via np.random.default_rng(seed). The advantage of passing a PRNG is that one can reuse that PRNG when calling spsa_grad multiple times, for instance during an optimization procedure.
- Deprecated in v0.32
- Removed in v0.33
The RandomLayers.compute_decomposition keyword argument ratio_imprivitive has been changed to ratio_imprim to match the call signature of the operation.
- Deprecated in v0.32
- Removed in v0.33
The QuantumScript.set_parameters method and the QuantumScript.data setter have been removed. Please use QuantumScript.bind_new_parameters instead.
- Deprecated in v0.32
- Removed in v0.33
The observables argument in QubitDevice.statistics is removed. Please use circuit instead. Using a list of observables in QubitDevice.statistics is removed. Please use a QuantumTape instead.
- Still accessible in v0.28-v0.31
- Removed in v0.32
The CV observables qml.X and qml.P have been removed. Use qml.QuadX and qml.QuadP instead.
- Deprecated in v0.32
- Removed in v0.33

The method tape.unwrap() and corresponding UnwrapTape and Unwrap classes are removed.

Deprecated in v0.32
Removed in v0.33

Instead of tape.unwrap(), use convert_to_numpy_parameters():

from pennylane.transforms import convert_to_numpy_parameters

qscript = qml.tape.QuantumTape([qml.RX(torch.tensor(0.1234), 0)],
                                 [qml.expval(qml.Hermitian(torch.eye(2), 0))] )
unwrapped_qscript = convert_to_numpy_parameters(qscript)

torch_params = qscript.get_parameters()
numpy_params = unwrapped_qscript.get_parameters()

qml.enable_return and qml.disable_return have been removed. The old return types are no longer available.
- Deprecated in v0.32
- Removed in v0.33
The mode keyword argument in QNode has been removed, as it was only used in the old return system (which has also been removed). Please use grad_on_execution instead.
- Deprecated in v0.32
- Removed in v0.33
qml.math.purity, qml.math.vn_entropy, qml.math.mutual_info, qml.math.fidelity, qml.math.relative_entropy, and qml.math.max_entropy no longer support state vectors as input. Please call qml.math.dm_from_state_vector on the input before passing to any of these functions.
- Still accepted in v0.31
- Removed in v0.32
The do_queue keyword argument in qml.operation.Operator has been removed. This affects all child classes, such as Operation, Observable, SymbolicOp and more. Instead of setting do_queue=False, use the qml.QueuingManager.stop_recording() context.
- Deprecated in v0.31
- Removed in v0.32
The qml.specs dictionary longer supports direct key access to certain keys. Instead these quantities can be accessed as fields of the new Resources object saved under specs_dict["resources"]:
- num_operations is no longer supported, use specs_dict["resources"].num_gates
- num_used_wires is no longer supported, use specs_dict["resources"].num_wires
- gate_types is no longer supported, use specs_dict["resources"].gate_types
- gate_sizes is no longer supported, use specs_dict["resources"].gate_sizes
- depth is no longer supported, use specs_dict["resources"].depth
These keys were still accessible in v0.31 and removed in v0.32.
qml.math.reduced_dm has been removed. Please use qml.math.reduce_dm or qml.math.reduce_statevector instead.
- Still accessible in v0.31
- Removed in v0.32
QuantumScript’s name keyword argument and property are removed. This also affects QuantumTape and OperationRecorder.
- Deprecated in v0.31
- Removed in v0.32
The Operation.base_name property is removed. Please use Operator.name or type(obj).__name__ instead.
- Still accessible in v0.31
- Removed in v0.32
LieAlgebraOptimizer has been renamed. Please use RiemannianGradientOptimizer instead.
- Deprecated in v0.31
- Removed in v0.32

The grouping_type and grouping_method arguments of qchem.molecular_hamiltonian() are removed.

Deprecated in v0.31
Removed in v0.32

Instead, simply construct a new instance of Hamiltonian with the grouping specified:

H, qubits = molecular_hamiltonian(symbols, coordinates)
grouped_h = qml.Hamiltonian(
    H.coeffs,
    H.ops,
    grouping_type=grouping_type,
    groupingmethod=grouping_method,
)

zyz_decomposition and xyx_decomposition are removed, use one_qubit_decomposition with a rotations keyword instead.
- Deprecated in v0.31
- Removed in v0.32
The qml.utils.sparse_hamiltonian function has been removed. ~.Hamiltonian.sparse_matrix should be used instead.
- Deprecated in v0.29
- Removed in v0.31
The collections module has been removed.
- Deprecated in v0.29
- Removed in v0.31
qml.op_sum has been removed. Users should use qml.sum instead.
- Deprecated in v0.29.
- Removed in v0.31.
The argument argnum for gradient transforms using the Jax interface is replaced by argnums.
- argnum is automatically changed to argnums for gradient transforms using JAX and a warning is raised in v0.30
- argnums is the only option for gradient transforms using JAX in v0.31
Evolution now adds a -1 to the input parameter. Beforehand, the minus sign was not included.
- Transition warning added in v0.29.
- Updated to current behaviour in v0.30.
The seed_recipes argument in qml.classical_shadow and qml.shadow_expval has been removed. An argument seed which defaults to None can contain an integer with the wanted seed.
- Still accessible in v0.28, v0.29
- Removed in v0.30
The get_operation tape method is updated to return the operation index as well, changing its signature.
- The new signature is available by changing the arg return_op_index to True in v0.29
- The old signature is replaced with the new one in v0.30
The grouping module has been removed. The functionality has been moved and reorganized in the new pauli module under pauli/utils.py or pauli/grouping/.
- Still accessible in v0.27, v0.28, v0.29, v0.30
- Removed in v0.31
The functions from grouping/pauli.py, grouping/transformations.py and grouping/utils.py have been moved to pauli/utils.py. The remaining functions have been consolidated in the pauli/grouping/ directory.
qml.VQECost is removed.
- Deprecated in 0.13
- Removed in 0.29

In-place inversion — op.inv() and op.inverse=value — is deprecated. Please use qml.adjoint or qml.pow instead.

Still accessible in v0.27 and v0.28
Removed in v0.29

Don’t use:

>>> v1 = qml.PauliX(0).inv()
>>> v2 = qml.PauliX(0)
>>> v2.inverse = True

Instead, use:

>>> qml.adjoint(qml.PauliX(0))
Adjoint(PauliX(wires=[0]))
>>> qml.pow(qml.PauliX(0), -1)
PauliX(wires=[0])**-1
>>> qml.pow(qml.PauliX(0), -1, lazy=False)
PauliX(wires=[0])
>>> qml.PauliX(0) ** -1
PauliX(wires=[0])**-1

The qml.utils.decompose_hamiltonian() method is removed. Please use qml.pauli_decompose().
- Still accessible in v0.27
- Removed in v0.28
qml.tape.get_active_tape is deprecated. Please use qml.QueuingManager.active_context() instead.
- Deprecated in v0.27
- Removed in v0.28
qml.transforms.qcut.remap_tape_wires is deprecated. Please use qml.map_wires instead.
- Deprecated in v0.27
- Removed in v0.28
QuantumTape.inv() is deprecated. Please use QuantumTape.adjoint() instead. This method returns a new tape instead of modifying itself in-place.
- Deprecated in v0.27
- Removed in v0.28
qml.tape.stop_recording and QuantumTape.stop_recording are moved to qml.QueuingManager.stop_recording
- Deprecated in v0.27
- Removed in v0.28
QueuingContext is renamed QueuingManager.
- Deprecated name QueuingContext in v0.27
- Removed in v0.28
QueuingManager.safe_update_info and AnnotateQueue.safe_update_info are removed.
- Deprecated in v0.27
- Removed in v0.28
ObservableReturnTypes Sample, Variance, Expectation, Probability, State, and MidMeasure are moved to measurements from operation.
- Deprecated in v0.23
- Removed in v0.27
The qml.utils.expand function is deprecated. qml.math.expand_matrix should be used instead.
- Deprecated in v0.24
- Removed in v0.27
The qml.Operation.get_parameter_shift method is removed. Use the methods of the gradients module for general parameter-shift rules instead.
- Deprecated in v0.22
- Removed in v0.28
qml.transforms.measurement_grouping has been removed. Please use qml.transforms.hamiltonian_expand instead.
- Deprecated in v0.28
- Removed in v0.29
qml.transforms.make_tape was previously deprecated, but there is no longer a plan to remove it. It no longer raises a warning, and the functionality is unchanged.
- Deprecated in v0.28
- Un-deprecated in v0.29

development/deprecations

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Deprecations¶

Pending deprecations¶

Completed removal of legacy operator arithmetic¶

Completed deprecation cycles¶

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