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

)

* Add support for v2 provider interface

In 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#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#5086

* Fix import path

* fix style

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

qiskit/aqua/algorithms/amplitude_amplifiers/grover.py

@@ -20,6 +20,7 @@
 
 from qiskit import ClassicalRegister, QuantumCircuit
 from qiskit.circuit.library import GroverOperator
+from qiskit.providers import Backend
 from qiskit.providers import BaseBackend
 from qiskit.quantum_info import Statevector
 
@@ -121,7 +122,7 @@ class Grover(QuantumAlgorithm):
         ('post_processing', {float: 'lam'}),
         ('grover_operator', {list: 'rotation_counts'}),
         ('quantum_instance', {str: 'mct_mode'}),
-        ('incremental', {(BaseBackend, QuantumInstance): 'quantum_instance'})
+        ('incremental', {(Backend, BaseBackend, QuantumInstance): 'quantum_instance'})
     ], skip=1)  # skip the argument 'self'
     def __init__(self,
                  oracle: Union[Oracle, QuantumCircuit, Statevector],
@@ -131,7 +132,7 @@ def __init__(self,
                  sample_from_iterations: bool = False,
                  post_processing: Callable[[List[int]], List[int]] = None,
                  grover_operator: Optional[QuantumCircuit] = None,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None,
+                 quantum_instance: Optional[Union[QuantumInstance, Backend, BaseBackend]] = None,
                  init_state: Optional[InitialState] = None,
                  incremental: bool = False,
                  num_iterations: Optional[int] = None,

qiskit/aqua/algorithms/factorizers/shor.py

@@ -23,6 +23,7 @@
 from qiskit.circuit import Gate, Instruction, ParameterVector
 from qiskit.circuit.library import QFT
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance
 from qiskit.aqua.algorithms import AlgorithmResult, QuantumAlgorithm
 from qiskit.aqua.utils import get_subsystem_density_matrix, summarize_circuits
@@ -53,7 +54,8 @@ class Shor(QuantumAlgorithm):
     def __init__(self,
                  N: int = 15,
                  a: int = 2,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None) -> None:
+                 quantum_instance: Optional[
+                     Union[QuantumInstance, BaseBackend, Backend]] = None) -> None:
         """
         Args:
             N: The integer to be factored, has a min. value of 3.

qiskit/aqua/algorithms/minimum_eigen_solvers/qaoa/qaoa.py

@@ -17,6 +17,7 @@
 import numpy as np
 
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance
 from qiskit.aqua.operators import OperatorBase, ExpectationBase, LegacyBaseOperator
 from qiskit.aqua.components.initial_states import InitialState
@@ -74,7 +75,8 @@ def __init__(self,
                  aux_operators: Optional[List[Optional[Union[OperatorBase, LegacyBaseOperator]]]] =
                  None,
                  callback: Optional[Callable[[int, np.ndarray, float, float], None]] = None,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None) -> None:
+                 quantum_instance: Optional[
+                     Union[QuantumInstance, BaseBackend, Backend]] = None) -> None:
         """
         Args:
             operator: Qubit operator

qiskit/aqua/algorithms/minimum_eigen_solvers/vqe.py

@@ -25,6 +25,7 @@
 from qiskit.circuit import Parameter
 from qiskit.circuit.library import RealAmplitudes
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance, AquaError
 from qiskit.aqua.algorithms import QuantumAlgorithm
 from qiskit.aqua.operators import (OperatorBase, ExpectationBase, ExpectationFactory, StateFn,
@@ -96,7 +97,8 @@ def __init__(self,
                  aux_operators: Optional[List[Optional[Union[OperatorBase,
                                                              LegacyBaseOperator]]]] = None,
                  callback: Optional[Callable[[int, np.ndarray, float, float], None]] = None,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None) -> None:
+                 quantum_instance: Optional[
+                     Union[QuantumInstance, BaseBackend, Backend]] = None) -> None:
         """
 
         Args:
@@ -200,7 +202,8 @@ def _set_expectation(self, exp: ExpectationBase) -> None:
         self._expect_op = None
 
     @QuantumAlgorithm.quantum_instance.setter
-    def quantum_instance(self, quantum_instance: Union[QuantumInstance, BaseBackend]) -> None:
+    def quantum_instance(self, quantum_instance: Union[QuantumInstance,
+                                                       BaseBackend, Backend]) -> None:
         """ set quantum_instance """
         super(VQE, self.__class__).quantum_instance.__set__(self, quantum_instance)
 

qiskit/aqua/algorithms/quantum_algorithm.py

@@ -21,6 +21,7 @@ class in this module.
 from abc import ABC, abstractmethod
 from typing import Union, Dict, Optional
 from qiskit.providers import BaseBackend
+from qiskit.providers.backend import Backend
 from qiskit.aqua import aqua_globals, QuantumInstance, AquaError
 
 
@@ -33,7 +34,8 @@ class QuantumAlgorithm(ABC):
     """
     @abstractmethod
     def __init__(self,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]]) -> None:
+                 quantum_instance: Optional[
+                     Union[QuantumInstance, Backend, BaseBackend, Backend]]) -> None:
         self._quantum_instance = None
         if quantum_instance:
             self.quantum_instance = quantum_instance
@@ -44,7 +46,8 @@ def random(self):
         return aqua_globals.random
 
     def run(self,
-            quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None,
+            quantum_instance: Optional[
+                Union[QuantumInstance, Backend, BaseBackend]] = None,
             **kwargs) -> Dict:
         """Execute the algorithm with selected backend.
 
@@ -59,7 +62,7 @@ def run(self,
         if quantum_instance is None and self.quantum_instance is None:
             raise AquaError("Quantum device or backend "
                             "is needed since you are running quantum algorithm.")
-        if isinstance(quantum_instance, BaseBackend):
+        if isinstance(quantum_instance, (BaseBackend, Backend)):
             self.set_backend(quantum_instance, **kwargs)
         else:
             if quantum_instance is not None:
@@ -77,23 +80,24 @@ def quantum_instance(self) -> Optional[QuantumInstance]:
         return self._quantum_instance
 
     @quantum_instance.setter
-    def quantum_instance(self, quantum_instance: Union[QuantumInstance, BaseBackend]) -> None:
+    def quantum_instance(self, quantum_instance: Union[QuantumInstance,
+                                                       BaseBackend, Backend]) -> None:
         """ Sets quantum instance. """
-        if isinstance(quantum_instance, BaseBackend):
+        if isinstance(quantum_instance, (BaseBackend, Backend)):
             quantum_instance = QuantumInstance(quantum_instance)
         self._quantum_instance = quantum_instance
 
-    def set_backend(self, backend: BaseBackend, **kwargs) -> None:
+    def set_backend(self, backend: Union[Backend, BaseBackend], **kwargs) -> None:
         """ Sets backend with configuration. """
         self.quantum_instance = QuantumInstance(backend)
         self.quantum_instance.set_config(**kwargs)
 
     @property
-    def backend(self) -> BaseBackend:
+    def backend(self) -> Union[Backend, BaseBackend]:
         """ Returns backend. """
         return self.quantum_instance.backend
 
     @backend.setter
-    def backend(self, backend: BaseBackend):
+    def backend(self, backend: Union[Backend, BaseBackend]):
         """ Sets backend without additional configuration. """
         self.set_backend(backend)

qiskit/aqua/algorithms/vq_algorithm.py

@@ -29,6 +29,7 @@
 
 from qiskit.circuit import QuantumCircuit, ParameterVector
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.aqua import QuantumInstance
 from qiskit.aqua.algorithms import AlgorithmResult, QuantumAlgorithm
 from qiskit.aqua.components.optimizers import Optimizer, SLSQP
@@ -47,7 +48,8 @@ def __init__(self,
                  optimizer: Optimizer,
                  cost_fn: Optional[Callable] = None,
                  initial_point: Optional[np.ndarray] = None,
-                 quantum_instance: Optional[Union[QuantumInstance, BaseBackend]] = None) -> None:
+                 quantum_instance: Optional[
+                     Union[QuantumInstance, BaseBackend, Backend]] = None) -> None:
         """
         Args:
             var_form: An optional parameterized variational form (ansatz).

qiskit/aqua/operators/converters/circuit_sampler.py

@@ -18,6 +18,7 @@
 from time import time
 
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.circuit import QuantumCircuit, Parameter, ParameterExpression
 from qiskit import QiskitError
 from qiskit.aqua import QuantumInstance
@@ -48,7 +49,7 @@ class CircuitSampler(ConverterBase):
     """
 
     def __init__(self,
-                 backend: Union[BaseBackend, QuantumInstance] = None,
+                 backend: Union[Backend, BaseBackend, QuantumInstance] = None,
                  statevector: Optional[bool] = None,
                  param_qobj: bool = False,
                  attach_results: bool = False) -> None:
@@ -101,7 +102,7 @@ def _check_quantum_instance_and_modes_consistent(self) -> None:
                              'backend, not {}.'.format(self.quantum_instance.backend))
 
     @property
-    def backend(self) -> BaseBackend:
+    def backend(self) -> Union[Backend, BaseBackend]:
         """ Returns the backend.
 
         Returns:
@@ -110,11 +111,11 @@ def backend(self) -> BaseBackend:
         return self.quantum_instance.backend
 
     @backend.setter
-    def backend(self, backend: BaseBackend):
+    def backend(self, backend: Union[Backend, BaseBackend]):
         """ Sets backend without additional configuration. """
         self.set_backend(backend)
 
-    def set_backend(self, backend: BaseBackend, **kwargs) -> None:
+    def set_backend(self, backend: Union[Backend, BaseBackend], **kwargs) -> None:
         """ Sets backend with configuration.
 
         Raises:
@@ -133,13 +134,14 @@ def quantum_instance(self) -> QuantumInstance:
         return self._quantum_instance
 
     @quantum_instance.setter
-    def quantum_instance(self, quantum_instance: Union[QuantumInstance, BaseBackend]) -> None:
+    def quantum_instance(self, quantum_instance: Union[QuantumInstance,
+                                                       Backend, BaseBackend]) -> None:
         """ Sets the QuantumInstance.
 
         Raises:
             ValueError: statevector or param_qobj are True when not supported by backend.
         """
-        if isinstance(quantum_instance, BaseBackend):
+        if isinstance(quantum_instance, (Backend, BaseBackend)):
             quantum_instance = QuantumInstance(quantum_instance)
         self._quantum_instance = quantum_instance
         self._check_quantum_instance_and_modes_consistent()

qiskit/aqua/operators/expectations/expectation_factory.py

@@ -17,6 +17,7 @@
 
 from qiskit import BasicAer
 from qiskit.providers import BaseBackend
+from qiskit.providers import Backend
 from qiskit.aqua.utils.backend_utils import (is_statevector_backend,
                                              is_aer_qasm,
                                              has_aer)
@@ -38,7 +39,7 @@ class ExpectationFactory:
 
     @staticmethod
     def build(operator: OperatorBase,
-              backend: Optional[Union[BaseBackend, QuantumInstance]] = None,
+              backend: Optional[Union[Backend, BaseBackend, QuantumInstance]] = None,
               include_custom: bool = True) -> ExpectationBase:
         """
         A factory method for convenient automatic selection of an Expectation based on the

qiskit/aqua/utils/run_circuits.py

@@ -21,6 +21,7 @@
 
 import numpy as np
 from qiskit.providers import BaseBackend, JobStatus, JobError
+from qiskit.providers import Backend
 from qiskit.providers.jobstatus import JOB_FINAL_STATES
 from qiskit.providers.basicaer import BasicAerJob
 from qiskit.qobj import QasmQobj
@@ -218,7 +219,7 @@ def run_qobj(qobj, backend, qjob_config=None, backend_options=None,
     backend_options = backend_options or {}
     noise_config = noise_config or {}
 
-    if backend is None or not isinstance(backend, BaseBackend):
+    if backend is None or not isinstance(backend, (Backend, BaseBackend)):
         raise ValueError('Backend is missing or not an instance of BaseBackend')
 
     with_autorecover = not is_simulator_backend(backend)