# Deprecations¶

All PennyLane deprecations will raise a `qml.PennyLaneDeprecationWarning`

. Pending and completed
deprecations are listed below.

## Pending deprecations¶

All of the legacy devices (any with the name

`default.qubit.{autograd,torch,tf,jax,legacy}`

) are deprecated. Use`default.qubit`

instead, as it supports backpropagation for the many backends the legacy devices support.Deprecated in v0.38

Will be removed in v0.39

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`

.Deprecated in v0.38

Will be removed in v0.39

The

`decomp_depth`

argument in`qml.device`

is deprecated.Deprecated in v0.38

Will be removed in v0.39

The

`max_expansion`

argument in`qml.QNode`

is deprecated.Deprecated in v0.38

Will be removed in v0.39

The functions

`qml.transforms.sum_expand`

and`qml.transforms.hamiltonian_expand`

are deprecated. Instead,`qml.transforms.split_non_commuting`

can be used for equivalent behaviour.Deprecated in v0.38

Will be removed in v0.39

The

`expansion_strategy`

attribute of`qml.QNode`

is deprecated. Users should make use of`qml.workflow.construct_batch`

, should they require fine control over the output tape(s).Deprecated in v0.38

Will be removed in v0.39

The

`expansion_strategy`

argument in`qml.specs`

,`qml.draw`

, and`qml.draw_mpl`

is deprecated. Instead, use the`level`

argument which provides a superset of options.Deprecated in v0.38

Will be removed in v0.39

The

`expand_fn`

argument in`qml.execute`

is deprecated. 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

Will be removed in v0.39

The

`max_expansion`

argument in`qml.execute`

is deprecated. 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

Will be removed in v0.39

The

`override_shots`

argument in`qml.execute`

is deprecated. Instead, please add the shots to the`QuantumTape`

s to be executed.Deprecated in v0.38

Will be removed in v0.39

The

`device_batch_transform`

argument in`qml.execute`

is deprecated. 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

Will be removed in v0.39

The functions

`qml.qinfo.classical_fisher`

and`qml.qinfo.quantum_fisher`

are deprecated since they are being migrated to the`qml.gradients`

module. Therefore,`qml.gradients.classical_fisher`

and`qml.gradients.quantum_fisher`

should be used instead.Deprecated and Duplicated in v0.38

Will be removed in v0.39

The

`simplify`

argument in`qml.Hamiltonian`

and`qml.ops.LinearCombination`

is deprecated. Instead,`qml.simplify()`

can be called on the constructed operator.Deprecated in v0.37

Will be removed in v0.39

### New operator arithmetic deprecations¶

The v0.36 release completes the main phase of PennyLane’s switchover to an updated approach for handling
arithmetic operations between operators, check out the Updated operators page
for more details. The old system is still accessible via `disable_new_opmath()`

. However, the
old system will be removed in an upcoming release and should be treated as deprecated. The following
functionality will explicitly raise a deprecation warning when used:

`op.ops`

and`op.coeffs`

will be deprecated in the future. Use`terms()`

instead.Added and deprecated for

`Sum`

and`Prod`

instances in v0.35

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, using`qml.Hamiltonian`

is recommended because it dispatches to the`LinearCombination`

class when the new approach to operator arithmetic is enabled. This will allow you to continue to use`qml.Hamiltonian`

with existing code without needing to make any changes.Use of

`qml.ops.Hamiltonian`

is deprecated in v0.36

Accessing terms of a tensor product (e.g.,

`op = X(0) @ X(1)`

) via`op.obs`

is deprecated with new operator arithmetic. A user should use`op.operands`

instead.Deprecated in v0.36

### Other deprecations¶

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 v0.36Fully migrated to

`manylinux_2_28`

with v0.37

`MultiControlledX`

is the only controlled operation that still supports specifying control values with a bit string. In the future, it will no longer accepts strings as control values.Deprecated in v0.36

Will be removed in v0.37

## Completed deprecation cycles¶

`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 v0.29The 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 v0.27Removed 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