Merge branch 'master' into rmv-qnode-static-methods

doc/development/deprecations.rst

@@ -9,12 +9,6 @@ deprecations are listed below.
 Pending deprecations
 --------------------
 
-* The ``qsvt_legacy`` function has been deprecated.
-  Instead, use ``qml.qsvt``. The new functionality takes an input polynomial instead of angles.
-
-  - Deprecated in v0.40
-  - Will be removed in v0.41
-
 * The ``tape`` and ``qtape`` properties of ``QNode`` have been deprecated. 
   Instead, use the ``qml.workflow.construct_tape`` function.
 
@@ -31,11 +25,6 @@ Pending deprecations
   - Deprecated in v0.40
   - Will be removed in v0.41
 
-* The ``output_dim`` property of ``qml.tape.QuantumScript`` has been deprecated. Instead, use method ``shape`` of ``QuantumScript`` or ``MeasurementProcess`` to get the same information.
-
-  - Deprecated in v0.40
-  - Will be removed in v0.41
-
 * The ``gradient_fn`` keyword argument to ``qml.execute`` has been renamed ``diff_method``.
 
   - Deprecated in v0.40
@@ -86,6 +75,17 @@ Completed deprecation cycles
 
 * 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

doc/releases/changelog-0.40.0.md

@@ -1170,4 +1170,4 @@ Anton Naim Ibrahim,
 Andrija Paurevic,
 Justin Pickering,
 Jay Soni,
-David Wierichs.
+David Wierichs.

doc/releases/changelog-dev.md

@@ -6,12 +6,21 @@
 
 <h3>Improvements 🛠</h3>
 
+* The coefficients of observables now have improved differentiability.
+  [(#6598)](https://github.com/PennyLaneAI/pennylane/pull/6598)
+
 <h3>Breaking changes 💔</h3>
 
 * The ``QNode.get_best_method`` and ``QNode.best_method_str`` methods have been removed. 
   Instead, use the ``qml.workflow.get_best_diff_method`` function. 
   [(#6823)](https://github.com/PennyLaneAI/pennylane/pull/6823)
 
+* The `output_dim` property of `qml.tape.QuantumScript` has been removed. Instead, use method `shape` of `QuantumScript` or `MeasurementProcess` to get the same information.
+  [(#6829)](https://github.com/PennyLaneAI/pennylane/pull/6829)
+
+* Removed method `qsvt_legacy` along with its private helper `_qsp_to_qsvt`
+  [(#6827)](https://github.com/PennyLaneAI/pennylane/pull/6827)
+
 <h3>Deprecations 👋</h3>
 
 <h3>Documentation 📝</h3>
@@ -24,4 +33,7 @@
 <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
-Diksha Dhawan
+
+Yushao Chen,
+Diksha Dhawan,
+Christina Lee,

pennylane/_version.py

@@ -16,4 +16,4 @@
 Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.41.0-dev6"
+__version__ = "0.41.0-dev7"

pennylane/compiler/compiler.py

@@ -23,7 +23,7 @@
 
 from packaging.version import Version
 
-PL_CATALYST_MIN_VERSION = Version("0.9.0")
+PL_CATALYST_MIN_VERSION = Version("0.10.0")
 
 
 class CompileError(Exception):

pennylane/devices/_legacy_device.py

@@ -93,7 +93,6 @@ def _local_tape_expand(tape, depth, stop_at):
 
     # Update circuit info
     new_tape._batch_size = tape._batch_size
-    new_tape._output_dim = tape._output_dim
     return new_tape
 
 

pennylane/gradients/parameter_shift.py

@@ -752,6 +752,12 @@ def _param_shift_stopping_condition(op) -> bool:
     return True
 
 
+def _inplace_set_trainable_params(tape):
+    """Update all the trainable params in place."""
+    params = tape.get_parameters(trainable_only=False)
+    tape.trainable_params = qml.math.get_trainable_indices(params)
+
+
 def _expand_transform_param_shift(
     tape: QuantumScript,
     argnum=None,
@@ -769,11 +775,21 @@ def _expand_transform_param_shift(
         name="param_shift",
         error=qml.operation.DecompositionUndefinedError,
     )
-    if new_tape is tape:
-        return [tape], postprocessing
-    params = new_tape.get_parameters(trainable_only=False)
-    new_tape.trainable_params = qml.math.get_trainable_indices(params)
-    return [new_tape], postprocessing
+    if any(
+        qml.math.requires_grad(d) for mp in tape.measurements for d in getattr(mp.obs, "data", [])
+    ):
+        try:
+            batch, postprocessing = qml.transforms.split_to_single_terms(new_tape)
+        except RuntimeError as e:
+            raise ValueError(
+                "Can only differentiate Hamiltonian "
+                f"coefficients for expectations, not {tape.measurements}."
+            ) from e
+    else:
+        batch = [new_tape]
+    if len(batch) > 1 or batch[0] is not tape:
+        _ = [_inplace_set_trainable_params(t) for t in batch]
+    return batch, postprocessing
 
 
 @partial(

pennylane/ops/functions/dot.py

@@ -142,10 +142,12 @@ def dot(
                 f"ops must be an Iterable of {t.__name__}'s, not a {t.__name__} itself."
             )
 
-    if len(coeffs) != len(ops):
-        raise ValueError("Number of coefficients and operators does not match.")
-    if len(coeffs) == 0 and len(ops) == 0:
-        raise ValueError("Cannot compute the dot product of an empty sequence.")
+    # tensorflow variables have no len
+    if qml.math.get_interface(coeffs) != "tensorflow":
+        if len(coeffs) != len(ops):
+            raise ValueError("Number of coefficients and operators does not match.")
+        if len(coeffs) == 0 and len(ops) == 0:
+            raise ValueError("Cannot compute the dot product of an empty sequence.")
 
     for t in (Operator, PauliWord, PauliSentence):
         if isinstance(ops, t):

pennylane/ops/op_math/sprod.py

@@ -15,7 +15,6 @@
 This file contains the implementation of the SProd class which contains logic for
 computing the scalar product of operations.
 """
-from copy import copy
 from typing import Union
 
 import pennylane as qml
@@ -148,7 +147,6 @@ def __init__(
         elif (base_pauli_rep := getattr(self.base, "pauli_rep", None)) and (
             self.batch_size is None
         ):
-            scalar = copy(self.scalar)
 
             pr = {pw: qnp.dot(coeff, scalar) for pw, coeff in base_pauli_rep.items()}
             self._pauli_rep = qml.pauli.PauliSentence(pr)

pennylane/tape/qscript.py

@@ -25,7 +25,7 @@
 from typing import Any, Optional, TypeVar, Union
 
 import pennylane as qml
-from pennylane.measurements import MeasurementProcess, ProbabilityMP, StateMP
+from pennylane.measurements import MeasurementProcess
 from pennylane.measurements.shots import Shots, ShotsLike
 from pennylane.operation import _UNSET_BATCH_SIZE, Observable, Operation, Operator
 from pennylane.pytrees import register_pytree
@@ -183,7 +183,6 @@ def __init__(
         self._trainable_params = trainable_params
         self._graph = None
         self._specs = None
-        self._output_dim = None
         self._batch_size = _UNSET_BATCH_SIZE
 
         self._obs_sharing_wires = None
@@ -322,29 +321,6 @@ def batch_size(self) -> Optional[int]:
             self._update_batch_size()
         return self._batch_size
 
-    @property
-    def output_dim(self) -> int:
-        """The (inferred) output dimension of the quantum script.
-
-        .. warning::
-
-            ``QuantumScript.output_dim`` is being deprecated. Instead, considering
-            using method ``shape`` of ``QuantumScript`` or ``MeasurementProcess``
-            to get the same information. See ``qml.gradients.parameter_shift_cv.py::_get_output_dim``
-            for an example.
-
-        """
-        # pylint: disable=import-outside-toplevel
-        import warnings
-
-        warnings.warn(
-            "The 'output_dim' property is deprecated and will be removed in version 0.41",
-            qml.PennyLaneDeprecationWarning,
-        )
-        if self._output_dim is None:
-            self._update_output_dim()  # this will set _batch_size if it isn't already
-        return self._output_dim
-
     @property
     def diagonalizing_gates(self) -> list[Operation]:
         """Returns the gates that diagonalize the measured wires such that they
@@ -566,28 +542,6 @@ def _update_batch_size(self):
 
         self._batch_size = candidate
 
-    def _update_output_dim(self):
-        """Update the dimension of the output of the quantum script.
-
-        Sets:
-            self._output_dim (int): Size of the quantum script output (when flattened)
-
-        This method makes use of `self.batch_size`, so that `self._batch_size`
-        needs to be up to date when calling it.
-        Call `_update_batch_size` before `_update_output_dim`
-        """
-        self._output_dim = 0
-        for m in self.measurements:
-            # attempt to infer the output dimension
-            if isinstance(m, ProbabilityMP):
-                # TODO: what if we had a CV device here? Having the base as
-                # 2 would have to be swapped to the cutoff value
-                self._output_dim += 2 ** len(m.wires)
-            elif not isinstance(m, StateMP):
-                self._output_dim += 1
-        if self.batch_size:
-            self._output_dim *= self.batch_size
-
     # ========================================================
     # Parameter handling
     # ========================================================
@@ -984,9 +938,6 @@ def copy(self, copy_operations: bool = False, **update) -> "QuantumScript":
             # obs may change if measurements were updated
             new_qscript._obs_sharing_wires = self._obs_sharing_wires
             new_qscript._obs_sharing_wires_id = self._obs_sharing_wires_id
-        if not (update.get("measurements") or update.get("operations")):
-            # output_dim may change if either measurements or operations were updated
-            new_qscript._output_dim = self._output_dim
         return new_qscript
 
     def __copy__(self) -> "QuantumScript":

pennylane/tape/tape.py

@@ -294,7 +294,6 @@ def stop_at(obj):  # pylint: disable=unused-argument
 
     # Update circuit info
     new_tape._batch_size = tape._batch_size
-    new_tape._output_dim = tape._output_dim
     return new_tape
 
 
@@ -343,7 +342,6 @@ def expand_tape_state_prep(tape, skip_first=True):
 
     # Update circuit info
     new_tape._batch_size = tape._batch_size
-    new_tape._output_dim = tape._output_dim
     return new_tape
 
 

pennylane/templates/subroutines/__init__.py

@@ -33,7 +33,7 @@
 from .hilbert_schmidt import HilbertSchmidt, LocalHilbertSchmidt
 from .flip_sign import FlipSign
 from .basis_rotation import BasisRotation
-from .qsvt import poly_to_angles, QSVT, qsvt, qsvt_legacy, transform_angles
+from .qsvt import poly_to_angles, QSVT, qsvt, transform_angles
 from .select import Select
 from .qdrift import QDrift
 from .controlled_sequence import ControlledSequence