Merge branch 'master' into fermi-commute

doc/code/qml_qinfo.rst

@@ -4,6 +4,13 @@ qml.qinfo
 Overview
 --------
 
+.. warning::
+
+ The ``qinfo`` module is deprecated and scheduled to be removed in v0.40. Most quantum information transforms
+ are available as measurement processes (see the :mod:`~pennylane.measurements` module for more details).
+ Additionally, the transforms are also available as standalone functions in the :mod:`~pennylane.math` and
+ :mod:`~pennylane.gradients` modules.
+
 This module provides a collection of methods to return quantum information quantities from :class:`~.QNode`
 returning :func:`~pennylane.state`.
 
@@ -15,8 +22,4 @@ Transforms
 .. automodapi:: pennylane.qinfo.transforms
  :no-heading:
  :no-inherited-members:
- :skip: metric_tensor
- :skip: adjoint_metric_tensor
  :skip: transform
- :skip: classical_fisher
- :skip: quantum_fisher

doc/development/deprecations.rst

@@ -9,12 +9,18 @@ deprecations are listed below.
 Pending deprecations
 --------------------
 
+* The ``qml.qinfo`` module has been deprecated. Please see the respective functions in the ``qml.math`` and ``qml.measurements``
+ modules instead.
+
+ - Deprecated in v0.39
+ - Will be removed in v0.40
+
 * ``Device``, ``QubitDevice``, and ``QutritDevice`` will no longer be imported top level in v0.40. They instead
  we be available as ``qml.devices.LegacyDevice``, ``qml.devices.QubitDevice``, and ``qml.devices.QutritDevice``
  respectively.
 
  - Deprecated top level access in v0.39
- - Top level access removed in v0.40
+ - Top level access will be removed in v0.40
 
 * `QNode.gradient_fn` is deprecated. Please use `QNode.diff_method` instead. `QNode.get_gradient_fn` can also be used to
  process the diff method.
@@ -27,12 +33,6 @@ Pending deprecations
  - 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.
 
@@ -89,6 +89,12 @@ Other deprecations
 Completed deprecation cycles
 ----------------------------
 
+* 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.
 

doc/releases/changelog-dev.md

@@ -66,6 +66,10 @@
 
 <h3>Breaking changes 💔</h3>
 
+* 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.
+ [(#5911)](https://github.com/PennyLaneAI/pennylane/pull/5911)
+
 * Remove support for Python 3.9.
  [(#6223)](https://github.com/PennyLaneAI/pennylane/pull/6223)
 
@@ -96,6 +100,10 @@
 
 <h3>Deprecations 👋</h3>
 
+* The `qml.qinfo` module has been deprecated. Please see the respective functions in the `qml.math` and
+ `qml.measurements` modules instead.
+ [(#5911)](https://github.com/PennyLaneAI/pennylane/pull/5911)
+
 * The ``QubitStateVector`` template is deprecated.
  Instead, use ``StatePrep``.
  [(#6172)](https://github.com/PennyLaneAI/pennylane/pull/6172)
@@ -143,10 +151,12 @@ This release contains contributions from (in alphabetical order):
 Guillermo Alonso,
 Utkarsh Azad,
 Astral Cai,
+Isaac De Vlugt,
 Lillian M. A. Frederiksen,
 Pietropaolo Frisoni,
 Emiliano Godinez,
 Christina Lee,
 William Maxwell,
 Lee J. O'Riordan,
+Mudit Pandey,
 David Wierichs,

pennylane/devices/default_mixed.py

@@ -763,8 +763,9 @@ def execute(self, circuit, **kwargs):
  self.measured_wires = self.wires
  return super().execute(circuit, **kwargs)
  if isinstance(m, (VnEntropyMP, MutualInfoMP)):
- # VnEntropy, MutualInfo: Computed for the state prior to measurement. So, readout
- # error need not be applied on the corresponding device wires.
+ # VnEntropy, MutualInfo: Computed for the state
+ # prior to measurement. So, readout error need not be applied to the
+ # corresponding device wires.
  continue
  wires_list.append(m.wires)
  self.measured_wires = qml.wires.Wires.all_wires(wires_list)

pennylane/measurements/mutual_info.py

@@ -74,7 +74,7 @@ def circuit_mutual(x):
  using the classical backpropagation differentiation method (``diff_method="backprop"``)
  with a compatible device and finite differences (``diff_method="finite-diff"``).
 
- .. seealso:: :func:`~.vn_entropy`, :func:`pennylane.qinfo.transforms.mutual_info` and :func:`pennylane.math.mutual_info`
+ .. seealso:: :func:`~pennylane.vn_entropy`, :func:`pennylane.math.mutual_info`
  """
  wires0 = qml.wires.Wires(wires0)
  wires1 = qml.wires.Wires(wires1)

pennylane/measurements/purity.py

@@ -57,7 +57,7 @@ def circuit_purity(p):
  >>> circuit_purity(0.1)
  array(0.7048)
 
- .. seealso:: :func:`pennylane.qinfo.transforms.purity` and :func:`pennylane.math.purity`
+ .. seealso:: :func:`pennylane.math.purity`
  """
  wires = Wires(wires)
  return PurityMP(wires=wires)

pennylane/measurements/vn_entropy.py

@@ -61,11 +61,11 @@ def circuit_entropy(x):
 
  .. note::
 
- Calculating the derivative of :func:`~.vn_entropy` is currently supported when
+ Calculating the derivative of :func:`~pennylane.vn_entropy` is currently supported when
  using the classical backpropagation differentiation method (``diff_method="backprop"``)
  with a compatible device and finite differences (``diff_method="finite-diff"``).
 
- .. seealso:: :func:`pennylane.qinfo.transforms.vn_entropy` and :func:`pennylane.math.vn_entropy`
+ .. seealso:: :func:`pennylane.math.vn_entropy`
  """
  wires = Wires(wires)
  return VnEntropyMP(wires=wires, log_base=log_base)
@@ -74,7 +74,7 @@ def circuit_entropy(x):
 class VnEntropyMP(StateMeasurement):
  """Measurement process that computes the Von Neumann entropy of the system prior to measurement.
 
- Please refer to :func:`vn_entropy` for detailed documentation.
+ Please refer to :func:`~pennylane.vn_entropy` for detailed documentation.
 
  Args:
  wires (.Wires): The wires the measurement process applies to.

pennylane/qinfo/__init__.py

@@ -18,8 +18,6 @@
  vn_entropy,
  purity,
  mutual_info,
- classical_fisher,
- quantum_fisher,
  fidelity,
  relative_entropy,
  trace_distance,