Operator Flow (qiskit-community/qiskit-aqua#852)

* Add abelian property to opvecs and AbelianGrouper to operator init.

* Break up PauliCoB big clifford synthesis function into smaller ones.

* Add AbelianGrouper test.

* Add better input checking in primitives and remove unnecessary print.

* Fix coeffs bugs in pauli_cob.py.

* Reorganize pauli_cob. All tests pass, with grouping on and off.

* Change expectation_value backends to work through setters.

* Reorganize local_simulator_sampler.py a bit to use it in a test.

* Grouping Paulis works!! All tests pass.

* Add "compute TPB pauli" function to pauli_cob.

* Add WIP attempt at evolution over Abelian paulis.

* Fix trotter bug.

* Fix some other Trotter bugs.

* Add parameters to OpPaulis and test. Parameterized evolution passes!!!

* Add parameter binding for Op coefficients.

* Add parameter binding, and binding tests. Tests pass.

* Add division to Operators to make normalization convenient.

* Finish merging MinEigenSolver PR. All tests pass.

* Update QAOA, all tests pass!!

* Update some QAOA imports and typehints.

* Add QDrift trotterization method. All tests pass.

* Start migrating QPE, tests fail.

* fix spell

* fix almost all style errors

* fix copyright

* fix import cycles, changed to relative imports when possible

* relative imports

* Add bind_params to state_fn_circuit.py and op_circuit.py, and tests. Add list unrolling for param binding, and tests. Tests pass.

* Add param list handling for all Op types.

* Make OpVec printing nicer.

* Add op_converter to imports for better backwards compatibility.

* Add AerPauliExpectation tests. Tests pass. Issue with Aer though.

* Fix a few AerPauliExpectation bugs

* Start building toward parameterized Qobj.

* fix some lint errors

* fix some lint errors

* fix style

* fix copyright

* set style to defaults, fix aqua unit test loading

* change loading tests qpe/iqpe

* Fix OpPrimitive lint errors.

* Fix operator_base.py lint errors.

* Fix state_fn.py lint errors.

* Fix OpVec lint errors.

* Fix state_fn_circuit.py lint errors.

* Fix state_fn_dict.py lint errors.

* Fix state_fn_operator.py lint errors.

* Fix state_fn_vector.py lint errors. Tests pass.

* Fix QDrift test to deal with first Op in trotterization list being OpCircuit.

* Fix op_circuit.py lint errors.

* Fix op_pauli.py lint errors.

* Fix op_composition.py lint errors.

* Fix op_kron.py lint errors.

* Fix abelian_grouper.py lint errors. Tests pass.

* Fix pauli_cob.py lint errors. Tests pass.

* Fix Expectation lint errors. Tests pass.

* Fix circuit sampler lint errors. Tests pass.

* Fix other expectation lint errors. Tests pass.

* Fix trotterization lint errors. Tests pass.

* Add MatrixEvolution shell, fix evolution lint errors.

* Fix bug in evolution tests after fixing lint errors.

* Fix cyclic import for lint.

* fix pylint cyclic import error

* Make tests pass. Add aux_ops back to VQE, and make VQE and QAOA take old or new ops.

* fix spell and lint

* Fix swapping issue in evolution.

* Fix composition in OpEvolution.

* Fix add OpSum and kron OpKron in OpEvolution.

* Add to_opflow to legacy base_operator

* Clean OpCircuit and StateFnCircuit __str__

* Fix qaoa mixer.

* fix spell,style

* Ok now really all tests pass.

* add to_matrix_op() methods to ops.

* Start migrating NumpyEigensolver for Opflow

* Start removing back from op_primitive eval functions. All tests pass.

* Update eval logic (to be able to remove back) for operator_combos.

* Add to_matrix_op for OpMatrix and StateFnVector, and change some `if back`s to `if back is not None`

* Finish decoupling back args from evals. All tests pass.

* Remove back from eval logic.

* Remove back from eval. All tests pass.

* Change matrix_expectation.py to rely on to_matrix_op.

* Migrate numpy_eigen_solver.py and numpy_minimum_eigen_solver.

* Remove ToMatrixOp converter.

* set VQE _auto_conversion to False for now

* Add sampling and tests. Fix a rounding error in a test. Fix a not none error in numpy_eigen_solver.py.

* Add array methods to OpVec. Fix typo in OpPauli. Allow reverse_endianness in to_opflow for WeightedPauli.

* Make NumpyEigensolver return a StateFn in result.eigenstate.

* Fix flaky optimization tests. Fix OpVec so iterator interface works.

* Fix StateFnVector sampling. Fix sparse NumpyEigensolution. Fix some aux_op stuff. Fix some other things here and there. Please no more breakage.

* Change some sparsity stuff.

* fix spelling

* Typehints.

* More typehints

* fix copyright

* fix spelling

* More typehints, make globals immutable.

* fix style

* Rearrange tests, Add CZ to globals.

* Refactor some names.

* Rename OpEvolution to EvolutionOp. Tests pass.

* Rename primitive ops. All tests pass.

* Finish renamings.

* Test IBMQ Pauli expectation. All tests pass.

* Update spelling.

* Update Pauli to num_qubits.

* Updating some naming.

* Add diag support to fix knapsack issue.

* fix unit test

* fix unit test

* fix travis

* Turn half of Steve's comments.

* Fix some exponentiation things.

* Fix some exponentiation things.

* Add trotterization_factory. All tests pass.

* Add evolution_factory. All tests pass.

* Add circuit_sampler_factory. All tests pass.

* Rename get_primitives to primitive_strings. Turn some of Julien's changes.

* Only allow sample_circuits to accept circuit_ops. Tests pass.

* Turn more review changes

* fix spell, style

* Add matrix_op exp_i() into HamiltonianGate. Tests fail due to CircuitOp decompose() during composition. If commented out (line 158) tests pass.

* Change CircuitOp and StateFnCircuit to rely on QuantumCircuit instead of Instruction. All tests pass. Add to_circuit_op to relevant ops. Solves all the decompose issues.

* Add matrix_evolution and update QAOA to test matrix_op for cost operator. Add logic to update UCCSD to operator flow. Tests pass.

* Delete PauliToInstruction, as it's obsolete.

* Add to_pauli_op and tests. Tests pass.

* Fix composed_op.py eval bug

* Add sig digit rounding. VQE tests fail.

* better precision for sig digit rounding. Tests pass.

* Fix pep8, add comment

* Add to_circuit_op to statefns, making DictToCircuit mostly obsolete. Tests pass.

* fix cyclic imports

* fix numpy boolean to string coercion

* Update repr and a docstring.

* Make ExpectationValues into converters. Test pass.

* Fix bug from merge.

* Fix bugs, make Minus just a CircuitStateFn and not a ComposedOp.

* Uncomment HamiltonianGate

* Update lots of docstrings part I. Tests pass.

* fix docstring

* More docstrings. Change class.rst so docs are generated for some python operator overloads.

* Add navigation structure for docs to init files

* More docs.

* fix doctrings

* 1) Change local_simulator_sampler.py to circuit_sampler.py
2) Set up circuit_samplers directory to be removed.
3) Add IBMQ VQE test.
4) Change AerPauliExpectation and CircuitSampler to handle expval_measurement/snapshots correctly.

Tests pass.

* 1) Delete circuit_samplers.
2) Allow CircuitSampler to attach_results.

* Update Operator init

* Change Operator directory names. Tests pass.

* fix spell, docs

* Turn Expectations purely into converters. Tests pass.

* fix docs

* skip IBMQ test

* Add Converters docs. Tests pass.

* fix spell

* Add Evolutions docs. Tests pass.

* Add Expectation docs. Tests pass.

* fix spell

* Add StateFn docs. Tests pass.

* Fix typo.

* Add ListOp init docs.

* Fix some ordering

* Little docs edits.

* fix spell

* Little docs edits.

* 1) Add to_legacy_op to OperatorBase to allow non-migrated algos to accept new Operators.
2) Allow QPE and iQPE to accept new Operators, migrate tests. Tests pass.

* Fix typehints for minimum_eigen_solvers

* Make sure expectations can handle mixed observables.

* fix spell

* Turn some more of Steve's comments. Tests pass.

* Turn some more of Steve's comments. Fix a buncha parameter stuff, and make sure mixed Pauli evolution works.

* Turn some more of Steve's comments. Tests pass.

* Turn some comments, fix a QAOA bug.

* Try collapsing ListOp to_matrix a bit.

* Turn more comments, fix some bugs.

* Turn more comments, fix some bugs.

* Update ListOp docs.

* Update ListOp docs.

* Update ListOp docs.

* fix docstring

* Update minimum_eigen_solvers setter typehints.

* Add Changelog and tests for DictToCircuitSum.

* Update VQE's construct_circuit and some changelog elements.

* fix spell

* Allow MinEigenOptimizer to accept StateFn result in result.eigenstate.

* fix style

* Update changelog with more detail. Update VQE to call super.

* Typo

Co-authored-by: Manoel Marques <manoel@us.ibm.com>
Co-authored-by: woodsp <woodsp@us.ibm.com>

qiskit/aqua/quantum_instance.py

@@ -204,7 +204,7 @@ def __init__(self, backend,
         self._job_callback = job_callback
         logger.info(self)
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Overload string.
 
         Returns:
@@ -244,6 +244,10 @@ def transpile(self, circuits):
 
         return transpiled_circuits
 
+    def assemble(self, circuits):
+        """ assemble circuits """
+        return compiler.assemble(circuits, **self._run_config.to_dict())
+
     def execute(self, circuits, had_transpiled=False):
         """
         A wrapper to interface with quantum backend.
@@ -268,7 +272,7 @@ def execute(self, circuits, had_transpiled=False):
             circuits = self.transpile(circuits)
 
         # assemble
-        qobj = compiler.assemble(circuits, **self._run_config.to_dict())
+        qobj = self.assemble(circuits)
 
         if self._meas_error_mitigation_cls is not None:
             qubit_index, qubit_mappings = get_measured_qubits_from_qobj(qobj)
@@ -302,8 +306,8 @@ def execute(self, circuits, had_transpiled=False):
             if build_cals_matrix:
                 logger.info("Updating qobj with the circuits for measurement error mitigation.")
                 use_different_shots = not (
-                    self._meas_error_mitigation_shots is None or
-                    self._meas_error_mitigation_shots == self._run_config.shots)
+                    self._meas_error_mitigation_shots is None
+                    or self._meas_error_mitigation_shots == self._run_config.shots)
                 temp_run_config = copy.deepcopy(self._run_config)
                 if use_different_shots:
                     temp_run_config.shots = self._meas_error_mitigation_shots

qiskit/aqua/utils/subsystem.py

@@ -100,7 +100,7 @@ def get_subsystems_counts(complete_system_counts, post_select_index=None, post_s
         count = complete_system_counts[mixed_measurement]
         subsystem_measurements = mixed_measurement.split()
         for k, d_l in zip(subsystem_measurements, subsystems_counts):
-            if (post_select_index is None or
-                    subsystem_measurements[post_select_index] == post_select_flag):
+            if (post_select_index is None
+                    or subsystem_measurements[post_select_index] == post_select_flag):
                 d_l[k] += count
     return [dict(d) for d in subsystems_counts]