Alternating Ansatz Feature

[shahidee44]

Description

• Refactored QAOACircuitParams Class to allow for more flexible implementations of the mixer part of the circuit
• QAOACircuitParams initialization input parameter name change from mixer_hamiltonian to mixer_block. (To emphasise the possible different input types that is accepted by the input parameter.)
• mixer_block allows the user to specify a List of RotationGateMap objects that the user wishes to use for the mixer portion of his alternating ansatz circuit. (This input parameter still allows for an input Hamiltonian object)
• mixer_coeffs is an optional parameter that must to be filled if the user uses a List of RotationGateMap objects to specify the mixer_block.
• QAOACircuitParams have new attributes that allow the user to access information that used to be stored only with the Hamiltonian objects. These new attributes provide a new interface for users to access these information. Some of the values are recreated within the object to emulate what is expected since the mixer_block input accepts different object types.
• New methods in the HamiltonianMapper object that lets the mapper also work with a List of RotationGateMap objects.
• Change in RotationGateMap objects that makes the pauli_label attribute optional for initialization.
• Some convenience functions for creating common patterns with RotationGateMap objects.
• unittests for QAOACircuitParams
• Updates to some unittests for new QAOACircuitParams attributes.
• Unittests that specify mixer_hamiltonian as an input initialization parameter for QAOACircuitParams are updated to mixer_block
• Added Custom Mixer Example Notebook in examples
• Added Custom Mixer Example Notebook to documentation.

Checklist

• I have performed a self-review of my code.
• I have commented my code and used numpy-style docstrings
• I have made corresponding updates to the documentation.
• My changes generate no new warnings
• I have added/updated tests to make sure bugfix/feature works.
• New and existing unit tests pass locally with my changes.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

test_parameters_plot.py (Changed mixer_hamiltonian keyword with mixer_block )

[codecov]

Codecov Report

Merging #85 (c53c170) into dev (80b0b6b) will increase coverage by 0.09%.
The diff coverage is 70.39%.

@@            Coverage Diff             @@
##              dev      #85      +/-   ##
==========================================
+ Coverage   87.30%   87.40%   +0.09%     
==========================================
  Files          67       67              
  Lines        8924     9096     +172     
==========================================
+ Hits         7791     7950     +159     
- Misses       1133     1146      +13     

Impacted Files	Coverage Δ
openqaoa/backends/qpus/qaoa_braket_qpu.py	21.59% <0.00%> (-0.51%)	⬇️
tests/test_qpu_qiskit.py	11.01% <0.00%> (ø)
tests/test_qpu_braket.py	10.38% <6.97%> (-0.44%)	⬇️
tests/test_qpu_devices.py	33.33% <15.78%> (+2.89%)	⬆️
openqaoa/devices.py	48.92% <16.66%> (+0.34%)	⬆️
openqaoa/utilities.py	84.52% <16.66%> (-3.85%)	⬇️
openqaoa/qaoa_parameters/baseparams.py	82.60% <91.22%> (+2.60%)	⬆️
tests/test_parameters.py	99.62% <98.82%> (-0.38%)	⬇️
openqaoa/qaoa_parameters/extendedparams.py	90.06% <100.00%> (ø)
openqaoa/qaoa_parameters/fourierparams.py	91.89% <100.00%> (ø)
... and 5 more

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[vishal-ph]

The code looks functional, and implements what's needed to build custom mixer blocks! I am approving this PR. However, let's create a new branch after this merge to improve the documentation of some of the newly added functions @shahidee44