Merge branch 'master' into clean_state_prep

doc/code/qml.rst

@@ -6,4 +6,4 @@ qml
 .. automodapi:: pennylane
     :no-heading:
     :include-all-objects:
-    :skip: Version, SimpleSpec, plugin_devices, plugin_converters, default_config, reload, version_info, defaultdict
+    :skip: plugin_converters, default_config, version_info, defaultdict

doc/code/qml_tape.rst

@@ -67,4 +67,5 @@ and a reduction in unintended side effects, ``QuantumScript`` is strictly used i
 .. automodapi:: pennylane.tape
     :no-main-docstr:
     :include-all-objects:
+    :skip: QuantumTapeBatch
     :inheritance-diagram:

doc/development/deprecations.rst

@@ -9,6 +9,22 @@ 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 ``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.
 

doc/releases/changelog-dev.md

@@ -22,13 +22,20 @@
 
 * `SProd.terms` now flattens out the terms if the base is a multi-term observable.
   [(#5885)](https://github.com/PennyLaneAI/pennylane/pull/5885)
-  
+
 * A new method `to_mat` has been added to the `FermiWord` and `FermiSentence` classes, which allows
   computing the matrix representation of these Fermi operators.
   [(#5920)](https://github.com/PennyLaneAI/pennylane/pull/5920)
 
+* New functionality has been added to natively support exponential extrapolation when using the `mitigate_with_zne`. This allows
+  users to have more control over the error mitigation protocol without needing to add further dependencies.
+  [(#5972)](https://github.com/PennyLaneAI/pennylane/pull/5972)
+
 <h3>Improvements 🛠</h3>
 
+* Added the `compute_sparse_matrix` method for `qml.ops.qubit.BasisStateProjector`.
+  [(#5790)](https://github.com/PennyLaneAI/pennylane/pull/5790)
+
 * `StateMP.process_state` defines rules in `cast_to_complex` for complex casting, avoiding a superfluous state vector copy in Lightning simulations
   [(#5995)](https://github.com/PennyLaneAI/pennylane/pull/5995)
 
@@ -52,6 +59,51 @@
 * Molecules and Hamiltonians can now be constructed for all the elements present in the periodic table.
   [(#5821)](https://github.com/PennyLaneAI/pennylane/pull/5821)
 
+* `qml.for_loop` and `qml.while_loop` now fallback to standard Python control
+  flow if `@qjit` is not present, allowing the same code to work with and without
+  `@qjit` without any rewrites.
+  [(#6014)](https://github.com/PennyLaneAI/pennylane/pull/6014)
+
+  ```python
+  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()
+  ```
+
+  ```pycon
+  >>> print(qml.draw(circuit)(0.5, 3))
+  0: ──H──RX(0.50)─╭●────────╭●──────────────────────────────────────┤  Probs
+  1: ──H───────────╰RY(0.25)─│──────────RX(0.48)─╭●──────────────────┤  Probs
+  2: ──H─────────────────────╰RY(0.25)───────────╰RY(0.23)──RX(0.46)─┤  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)
+  ```
+
 * The `qubit_observable` function is modified to return an ascending wire order for molecular 
   Hamiltonians.
   [(#5950)](https://github.com/PennyLaneAI/pennylane/pull/5950)
@@ -87,6 +139,12 @@
 
 <h3>Deprecations 👋</h3>
 
+* The `decomp_depth` argument in `qml.device` has been deprecated.
+  [(#6026)](https://github.com/PennyLaneAI/pennylane/pull/6026)
+
+* The `max_expansion` argument in `qml.QNode` has been deprecated.
+  [(#6026)](https://github.com/PennyLaneAI/pennylane/pull/6026)
+
 * The `expansion_strategy` attribute in the `QNode` class is deprecated.
   [(#5989)](https://github.com/PennyLaneAI/pennylane/pull/5989)
 
@@ -126,6 +184,10 @@
   Instead, ``BasisState`` can be called on the constructed operator.
   [(#6021)](https://github.com/PennyLaneAI/pennylane/pull/6021)
 
+* The legacy devices `default.qubit.{autograd,torch,tf,jax,legacy}` are deprecated.
+  Instead, use `default.qubit` as it now supports backpropagation through the several backends.
+  [(#5997)](https://github.com/PennyLaneAI/pennylane/pull/5997)
+
 <h3>Documentation 📝</h3>
 
 * Improves the docstring for `QuantumScript.expand` and `qml.tape.tape.expand_tape`.
@@ -174,11 +236,13 @@ Lillian M. A. Frederiksen,
 Pietropaolo Frisoni,
 Emiliano Godinez,
 Renke Huang,
+Josh Izaac,
 Soran Jahangiri,
 Christina Lee,
 Austin Huang,
-Christina Lee,
 William Maxwell,
 Vincent Michaud-Rioux,
+Anurav Modak,
 Mudit Pandey,
-Erik Schultheis.
+Erik Schultheis,
+nate stemen.