Add support for v2 provider interface (qiskit-community/qiskit-aqua#1270)

* Add support for v2 provider interface

In Qiskit/qiskit#5086 the v2 provider interface is being added.
This starter interface is basically a drop in replacement for the v1
interface with 3 changes it's explicitly versioned at the object level,
Backend.run() can take in a circuit object, and Job objects can also be
async or sync. Eventually the interace will likely evolve towards a
model similar to what was initially done in Qiskit/qiskit#4885.
This commit adds initial support for v2 provider backend objects, the
explicit type checking for BaseBackend objects is blocking the terra PR
from moving forward (because it switched BasicAer to use the v2
interface). This initial support just means accepting v2 Backend objects
in addition to v1 BaseBackend objects.

Depends on Qiskit/qiskit#5086

* Fix import path

* fix style

Co-authored-by: Manoel Marques <[email protected]>

Author: mtreinish

qiskit/optimization/algorithms/grover_optimizer.py

@@ -23,6 +23,7 @@
 from qiskit.aqua import QuantumInstance, aqua_globals
 from qiskit.aqua.algorithms.amplitude_amplifiers.grover import Grover
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.circuit.library import QuadraticForm
 from .optimization_algorithm import (OptimizationResultStatus, OptimizationAlgorithm,
                                      OptimizationResult)
@@ -37,7 +38,7 @@ class GroverOptimizer(OptimizationAlgorithm):
     """Uses Grover Adaptive Search (GAS) to find the minimum of a QUBO function."""
 
     def __init__(self, num_value_qubits: int, num_iterations: int = 3,
-                 quantum_instance: Optional[Union[BaseBackend, QuantumInstance]] = None,
+                 quantum_instance: Optional[Union[BaseBackend, Backend, QuantumInstance]] = None,
                  converters: Optional[Union[QuadraticProgramConverter,
                                             List[QuadraticProgramConverter]]] = None,
                  penalty: Optional[float] = None) -> None:
@@ -76,13 +77,14 @@ def quantum_instance(self) -> QuantumInstance:
         return self._quantum_instance
 
     @quantum_instance.setter
-    def quantum_instance(self, quantum_instance: Union[BaseBackend, QuantumInstance]) -> None:
+    def quantum_instance(self, quantum_instance: Union[Backend,
+                                                       BaseBackend, QuantumInstance]) -> None:
         """Set the quantum instance used to run the circuits.
 
         Args:
             quantum_instance: The quantum instance to be used in the algorithm.
         """
-        if isinstance(quantum_instance, BaseBackend):
+        if isinstance(quantum_instance, (BaseBackend, Backend)):
             self._quantum_instance = QuantumInstance(quantum_instance)
         else:
             self._quantum_instance = quantum_instance