V0.21.0 master merger (#233)

* Update changelog and version

* Update CHANGELOG

* Add lightning v21 performance gains

* Add lightning performance comparison with previous release

* Update figure resolution

* Update changelog data

* Added example bm for latest lightning release

* Include C++ source files in binary wheels (#225)

* Include C++ source files in binary wheels

* Auto update version

* Auto update version

* Auto update version

Co-authored-by: Ali Asadi <ali@xanadu.ai>
Co-authored-by: Chae-Yeun Park <chae-yeun@xanadu.ai>

.github/CHANGELOG.md

@@ -39,37 +39,75 @@ Ali Asadi, Chae-Yeun Park
 # Release 0.21.0
 
 ### New features since last release
-* Direct support to probability, expectation value and variance calculation in PL-Lightning.
-[(#185)](https://github.com/PennyLaneAI/pennylane-lightning/pull/185)
 
 * Add C++ only benchmark for a given list of gates.
 [(#199)](https://github.com/PennyLaneAI/pennylane-lightning/pull/199)
 
+* Wheel-build support for Python 3.10.
+[(#186)](https://github.com/PennyLaneAI/pennylane-lightning/pull/186)
+
+* C++ support for probability, expectation value and variance calculations.
+[(#185)](https://github.com/PennyLaneAI/pennylane-lightning/pull/185)
+
 * Add bindings to C++ expval, var, probs.
 [(#214)](https://github.com/PennyLaneAI/pennylane-lightning/pull/214)
 
-### Breaking changes
-
 ### Improvements
 
-* Add a new C++ kernel. 
+* `setup.py` adds debug only when --debug is given
+[(#208)](https://github.com/PennyLaneAI/pennylane-lightning/pull/208)
+
+* Add new highly-performant C++ kernels for quantum gates. 
 [(#202)](https://github.com/PennyLaneAI/pennylane-lightning/pull/202)
 
+The new kernels significantly improve the runtime performance of PennyLane-Lightning 
+for both differentiable and non-differentiable workflows. Here is an example workflow
+using the adjoint differentiation method with a circuit of 5 strongly entangling layers:
+
+```python
+import pennylane as qml
+from pennylane import numpy as np
+from pennylane.templates.layers import StronglyEntanglingLayers
+from numpy.random import random
+np.random.seed(42)
+n_layers = 5
+n_wires = 6
+dev = qml.device("lightning.qubit", wires=n_wires)
+
+@qml.qnode(dev, diff_method="adjoint")
+def circuit(weights):
+    StronglyEntanglingLayers(weights, wires=list(range(n_wires)))
+    return [qml.expval(qml.PauliZ(i)) for i in range(n_wires)]
+
+init_weights = np.random.random(StronglyEntanglingLayers.shape(n_layers=n_layers, n_wires=n_wires))
+params = np.array(init_weights,requires_grad=True)
+jac = qml.jacobian(circuit)(params)
+```
+The latest release shows improved performance on both single and multi-threaded evaluations!
+
+<img src="https://raw.githubusercontent.com/PennyLaneAI/pennylane-lightning/v0.21.0-rc0/doc/_static/lightning_v20_v21_bm.png" width=50%/>
+
 * Ensure debug info is built into dynamic libraries.
 [(#201)](https://github.com/PennyLaneAI/pennylane-lightning/pull/201)
 
 ### Documentation
 
+* New guidelines on adding and benchmarking C++ kernels.
+[(#202)](https://github.com/PennyLaneAI/pennylane-lightning/pull/202)
+
 ### Bug fixes
 
-* Add virtual destructor to C++ state-vector classes.
-[(#200)](https://github.com/PennyLaneAI/pennylane-lightning/pull/200)
+* Update clang-format version
+[(#219)](https://github.com/PennyLaneAI/pennylane-lightning/pull/219)
+
+* Fix failed tests on Windows.
+[(#218)](https://github.com/PennyLaneAI/pennylane-lightning/pull/218)
 
 * Fix failed tests for the non-binary wheel.
 [(#213)](https://github.com/PennyLaneAI/pennylane-lightning/pull/213)
 
-* Fix failed tests on Windows.
-[(#218)](https://github.com/PennyLaneAI/pennylane-lightning/pull/218)
+* Add virtual destructor to C++ state-vector classes.
+[(#200)](https://github.com/PennyLaneAI/pennylane-lightning/pull/200)
 
 ### Contributors
 
@@ -129,9 +167,6 @@ Lee J. O'Riordan
 * Added examples folder containing aggregate gate performance test.
 [(#165)](https://github.com/PennyLaneAI/pennylane-lightning/pull/165)
 
-* Add VJP support to PL-Lightning.
-[(#181)](https://github.com/PennyLaneAI/pennylane-lightning/pull/181)
-
 ### Breaking changes
 
 ### Improvements

pennylane_lightning/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.22.0-dev7"
+__version__ = "0.22.0-dev8"