Pending deprecate algorithms (Qiskit#8703)

* Pending deprecate algorithms

* Update releasenotes/notes/pending-deprecate-min-eigen-solvers-fa4341e1014e4df0.yaml

Co-authored-by: Steve Wood <40241007+woodsp-ibm@users.noreply.github.com>

Co-authored-by: Steve Wood <40241007+woodsp-ibm@users.noreply.github.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit/algorithms/minimum_eigen_solvers/minimum_eigen_solver.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2020.
+# (C) Copyright IBM 2020, 2022.
 #
 # This code is licensed under the Apache License, Version 2.0. You may
 # obtain a copy of this license in the LICENSE.txt file in the root directory
@@ -18,18 +18,34 @@
 import numpy as np
 
 from qiskit.opflow import OperatorBase
+from qiskit.utils.deprecation import deprecate_function
 from ..algorithm_result import AlgorithmResult
 from ..list_or_dict import ListOrDict
 
 
 class MinimumEigensolver(ABC):
-    """The Minimum Eigensolver Interface.
+    """Pending deprecation: Minimum Eigensolver Interface.
+
+    The Minimum Eigensolver interface has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.MinimumEigensolver` interface.
+    This interface will be deprecated in a future release and subsequently
+    removed after that.
 
     Algorithms that can compute a minimum eigenvalue for an operator
     may implement this interface to allow different algorithms to be
     used interchangeably.
     """
 
+    @deprecate_function(
+        "The Minimum Eigensolver interface has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.MinimumEigensolver interface. "
+        "This interface will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
+    def __init__(self) -> None:
+        pass
+
     @abstractmethod
     def compute_minimum_eigenvalue(
         self, operator: OperatorBase, aux_operators: Optional[ListOrDict[OperatorBase]] = None
@@ -67,8 +83,22 @@ def supports_aux_operators(cls) -> bool:
 
 
 class MinimumEigensolverResult(AlgorithmResult):
-    """Minimum Eigensolver Result."""
+    """Pending deprecation: Minimum Eigensolver Result.
+
+    The MinimumEigensolverResult class has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.MinimumEigensolverResult` class.
+    This class will be deprecated in a future release and subsequently
+    removed after that.
+
+    """
 
+    @deprecate_function(
+        "The MinimumEigensolverResult class has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.MinimumEigensolverResult class. "
+        "This class will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
     def __init__(self) -> None:
         super().__init__()
         self._eigenvalue = None

qiskit/algorithms/minimum_eigen_solvers/numpy_minimum_eigen_solver.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2020.
+# (C) Copyright IBM 2020, 2022.
 #
 # This code is licensed under the Apache License, Version 2.0. You may
 # obtain a copy of this license in the LICENSE.txt file in the root directory
@@ -14,9 +14,11 @@
 
 from typing import List, Optional, Union, Callable
 import logging
+import warnings
 import numpy as np
 
 from qiskit.opflow import OperatorBase
+from qiskit.utils.deprecation import deprecate_function
 from ..eigen_solvers.numpy_eigen_solver import NumPyEigensolver
 from .minimum_eigen_solver import MinimumEigensolver, MinimumEigensolverResult
 from ..list_or_dict import ListOrDict
@@ -26,9 +28,22 @@
 
 class NumPyMinimumEigensolver(MinimumEigensolver):
     """
-    The Numpy Minimum Eigensolver algorithm.
+    Pending deprecation: Numpy Minimum Eigensolver algorithm.
+
+    The NumPyMinimumEigensolver class has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.NumPyMinimumEigensolver` class.
+    This class will be deprecated in a future release and subsequently
+    removed after that.
+
     """
 
+    @deprecate_function(
+        "The NumPyMinimumEigensolver class has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.NumPyMinimumEigensolver class. "
+        "This class will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
     def __init__(
         self,
         filter_criterion: Callable[
@@ -44,6 +59,9 @@ def __init__(
                 whether to consider this value or not. If there is no
                 feasible element, the result can even be empty.
         """
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            super().__init__()
         self._ces = NumPyEigensolver(filter_criterion=filter_criterion)
         self._ret = MinimumEigensolverResult()
 

qiskit/algorithms/minimum_eigen_solvers/qaoa.py

@@ -13,6 +13,7 @@
 """ The Quantum Approximate Optimization Algorithm. """
 
 from typing import List, Callable, Optional, Union
+import warnings
 import numpy as np
 
 from qiskit.algorithms.optimizers import Minimizer, Optimizer
@@ -22,13 +23,19 @@
 from qiskit.providers import Backend
 from qiskit.utils.quantum_instance import QuantumInstance
 from qiskit.utils.validation import validate_min
+from qiskit.utils.deprecation import deprecate_function
 from qiskit.circuit.library.n_local.qaoa_ansatz import QAOAAnsatz
 from qiskit.algorithms.minimum_eigen_solvers.vqe import VQE
 
 
 class QAOA(VQE):
     """
-    The Quantum Approximate Optimization Algorithm.
+    Pending deprecation: Quantum Approximate Optimization Algorithm.
+
+    The QAOA class has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.QAOA` class.
+    This class will be deprecated in a future release and subsequently
+    removed after that.
 
     `QAOA <https://arxiv.org/abs/1411.4028>`__ is a well-known algorithm for finding approximate
     solutions to combinatorial-optimization problems.
@@ -52,6 +59,13 @@ class QAOA(VQE):
     the evolution to a feasible subspace of the full Hilbert space.
     """
 
+    @deprecate_function(
+        "The QAOA class has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.QAOA class. "
+        "This class will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
     def __init__(
         self,
         optimizer: Optional[Union[Optimizer, Minimizer]] = None,
@@ -114,17 +128,19 @@ def __init__(
         self._initial_state = initial_state
         self._cost_operator = None
 
-        super().__init__(
-            ansatz=None,
-            optimizer=optimizer,
-            initial_point=initial_point,
-            gradient=gradient,
-            expectation=expectation,
-            include_custom=include_custom,
-            max_evals_grouped=max_evals_grouped,
-            callback=callback,
-            quantum_instance=quantum_instance,
-        )
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            super().__init__(
+                ansatz=None,
+                optimizer=optimizer,
+                initial_point=initial_point,
+                gradient=gradient,
+                expectation=expectation,
+                include_custom=include_custom,
+                max_evals_grouped=max_evals_grouped,
+                callback=callback,
+                quantum_instance=quantum_instance,
+            )
 
     def _check_operator_ansatz(self, operator: OperatorBase) -> OperatorBase:
         # Recreates a circuit based on operator parameter.

qiskit/algorithms/minimum_eigen_solvers/vqe.py

@@ -18,6 +18,7 @@
 from __future__ import annotations
 
 import logging
+import warnings
 from time import time
 from typing import Callable, Dict, List, Optional, Tuple, Union
 
@@ -40,6 +41,7 @@
 from qiskit.utils import QuantumInstance, algorithm_globals
 from qiskit.utils.backend_utils import is_aer_provider
 from qiskit.utils.validation import validate_min
+from qiskit.utils.deprecation import deprecate_function
 
 from ..aux_ops_evaluator import eval_observables
 from ..exceptions import AlgorithmError
@@ -52,7 +54,12 @@
 
 
 class VQE(VariationalAlgorithm, MinimumEigensolver):
-    r"""The Variational Quantum Eigensolver algorithm.
+    r"""Pending deprecation: Variational Quantum Eigensolver algorithm.
+
+    The VQE class has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.VQE` class.
+    This class will be deprecated in a future release and subsequently
+    removed after that.
 
     `VQE <https://arxiv.org/abs/1304.3061>`__ is a quantum algorithm that uses a
     variational technique to find
@@ -120,6 +127,13 @@ def my_minimizer(fun, x0, jac=None, bounds=None) -> OptimizerResult:
 
     """
 
+    @deprecate_function(
+        "The VQE class has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.VQE class. "
+        "This class will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
     def __init__(
         self,
         ansatz: Optional[QuantumCircuit] = None,
@@ -171,7 +185,9 @@ def __init__(
         """
         validate_min("max_evals_grouped", max_evals_grouped, 1)
 
-        super().__init__()
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            super().__init__()
 
         self._max_evals_grouped = max_evals_grouped
         self._circuit_sampler = None  # type: Optional[CircuitSampler]
@@ -641,10 +657,26 @@ def _get_eigenstate(self, optimal_parameters) -> Union[List[float], Dict[str, in
 
 
 class VQEResult(VariationalResult, MinimumEigensolverResult):
-    """VQE Result."""
+    """Pending deprecation: VQE Result.
+
+    The VQEResult class has been superseded by the
+    :class:`qiskit.algorithms.minimum_eigensolvers.VQEResult` class.
+    This class will be deprecated in a future release and subsequently
+    removed after that.
+
+    """
 
+    @deprecate_function(
+        "The VQEResult class has been superseded by the "
+        "qiskit.algorithms.minimum_eigensolvers.VQEResult class. "
+        "This class will be deprecated in a future release and subsequently "
+        "removed after that.",
+        category=PendingDeprecationWarning,
+    )
     def __init__(self) -> None:
-        super().__init__()
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            super().__init__()
         self._cost_function_evals = None
 
     @property