Differentiable parameter-shift gradient transform (#1479)

* more * more * more * more * more * add tests * more tests * more tests * changelog * add todo * fix * fix * fix * Apply suggestions from code review Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> * add parameter-shift * add parameter-shift * changes * fixes * fixes * suggested changes * linting * add tests * add tests * bug * remove stack * Apply suggestions from code review Co-authored-by: Maria Schuld <mariaschuld@gmail.com> * Update pennylane/gradients/finite_difference.py * more * suggested changes * suggested changes * typo * Apply suggestions from code review Co-authored-by: antalszava <antalszava@gmail.com> * suggested changes * Update pennylane/gradients/parameter_shift.py Co-authored-by: antalszava <antalszava@gmail.com> * suggested changes * Apply suggestions from code review Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> * Update pennylane/gradients/parameter_shift.py Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> * suggested changes * suggested changes * suggested changes * suggested changes * suggested changes * suggested changes * suggested changes * suggested changes * Apply suggestions from code review Co-authored-by: Maria Schuld <mariaschuld@gmail.com> * added multiplier test * Suggested changes * suggested changes * suggested changes * typo * Apply suggestions from code review Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> * suggested changes * Update tests/gradients/test_parameter_shift.py Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> Co-authored-by: Olivia Di Matteo <2068515+glassnotes@users.noreply.github.com> Co-authored-by: antalszava <antalszava@gmail.com> Co-authored-by: Maria Schuld <mariaschuld@gmail.com>
PennyLaneAI · Aug 3, 2021 · ab71001 · ab71001
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commit ab71001
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diff --git a/pennylane/gradients/__init__.py b/pennylane/gradients/__init__.py
@@ -15,5 +15,7 @@
 import pennylane as qml
 
 from . import finite_difference
+from . import parameter_shift
 
 from .finite_difference import finite_diff, finite_diff_coeffs, generate_shifted_tapes
+from .parameter_shift import param_shift
diff --git a/pennylane/gradients/finite_difference.py b/pennylane/gradients/finite_difference.py
@@ -16,12 +16,15 @@
 of a quantum tape.
 """
 # pylint: disable=protected-access,too-many-arguments
+import functools
+
 import numpy as np
 from scipy.special import factorial
 
 import pennylane as qml
 
 
+@functools.lru_cache(maxsize=None)
 def finite_diff_coeffs(n, approx_order, strategy):
     r"""Generate the finite difference shift values and corresponding
     term coefficients for a given derivative order, approximation accuracy,