Deprecate fake provider class and device-specific fake backends. Leav…

…e fake backend base classes and special fake backends for testing purposes.

qiskit/providers/fake_provider/fake_backend.py

@@ -73,6 +73,15 @@ class FakeBackendV2(BackendV2):
 
     def __init__(self):
         """FakeBackendV2 initializer."""
+        warnings.warn(
+            message="Device-specific fake backends have been migrated to the `qiskit_ibm_runtime` package. "
+            "These classes are deprecated as of qiskit 0.46.0 and will be removed in qiskit 1.0.0. "
+            "You should migrate your code to use "
+            "`from qiskit_ibm_runtime.fake_provider import FakeExample` "
+            "instead of `from qiskit.providers.fake_provider import FakeExample`.",
+            category=DeprecationWarning,
+            stacklevel=3,
+        )
         self._conf_dict = self._get_conf_dict_from_json()
         self._props_dict = None
         self._defs_dict = None

qiskit/providers/fake_provider/fake_backend_v2.py

@@ -32,11 +32,19 @@
 from qiskit.providers.options import Options
 from qiskit.transpiler import Target, InstructionProperties
 from qiskit.providers.basic_provider.basic_simulator import BasicSimulator
+from qiskit.utils.deprecation import deprecate_func
 
 
 class FakeBackendV2(BackendV2):
     """A mock backend that doesn't implement run() to test compatibility with Terra internals."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.basic_provider.GenericBackendV2` "
+        "class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         super().__init__(
             None,
@@ -111,6 +119,13 @@ def qubit_properties(self, qubit):
 class FakeBackend5QV2(BackendV2):
     """A mock backend that doesn't implement run() to test compatibility with Terra internals."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.basic_provider.GenericBackendV2` "
+        "class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self, bidirectional=True):
         super().__init__(
             None,
@@ -183,6 +198,13 @@ def run(self, run_input, **options):
 class FakeBackendSimple(BackendV2):
     """A fake simple backend that wraps BasicSimulator to implement run()."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.basic_provider.GenericBackendV2` "
+        "class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         super().__init__(
             None,

qiskit/providers/fake_provider/fake_job.py

@@ -19,13 +19,20 @@
 
 from qiskit.providers import JobV1
 from qiskit.providers.jobstatus import JobStatus
+from qiskit.utils.deprecation import deprecate_func
 
 
 class FakeJob(JobV1):
     """Fake simulator job"""
 
     _executor = futures.ThreadPoolExecutor()
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.JobV1` class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self, backend, job_id, fn):
         super().__init__(backend, job_id)
         self._backend = backend

qiskit/providers/fake_provider/fake_mumbai_v2.py

@@ -30,11 +30,19 @@
 from qiskit.providers.backend import BackendV2, QubitProperties
 from qiskit.providers.options import Options
 from qiskit.transpiler import Target, InstructionProperties
+from qiskit.utils.deprecation import deprecate_func
 
 
 class FakeMumbaiFractionalCX(BackendV2):
     """A fake mumbai backend."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.basic_provider.GenericBackendV2` "
+        "class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         super().__init__(
             name="FakeMumbaiFractionalCX",

qiskit/providers/fake_provider/fake_provider.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2019.
+# (C) Copyright IBM 2019, 2023.
 #
 # 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
@@ -18,6 +18,7 @@
 
 from qiskit.providers.provider import ProviderV1
 from qiskit.providers.exceptions import QiskitBackendNotFoundError
+from qiskit.utils.deprecation import deprecate_func
 
 from .backends import *
 from .fake_qasm_simulator import FakeQasmSimulator
@@ -28,6 +29,15 @@
 class FakeProviderFactory:
     """Fake provider factory class."""
 
+    @deprecate_func(
+        additional_msg="This class has been migrated to the `qiskit_ibm_runtime` package. "
+        "You should migrate your code to "
+        "use `from qiskit_ibm_runtime.fake_provider import FakeProviderExample` "
+        "instead of `from qiskit.providers.fake_provider import FakeProviderExample`.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         self.fake_provider = FakeProvider()
 
@@ -86,6 +96,14 @@ def get_backend(self, name=None, **kwargs):
     def backends(self, name=None, **kwargs):
         return self._backends
 
+    @deprecate_func(
+        additional_msg="This class has been migrated to the `qiskit_ibm_runtime` package. "
+        "You should migrate your code to "
+        "use `from qiskit_ibm_runtime.fake_provider import FakeProviderExample` "
+        "instead of `from qiskit.providers.fake_provider import FakeProviderExample`.",
+        since="0.46.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         self._backends = [
             FakeAlmadenV2(),
@@ -160,6 +178,14 @@ def get_backend(self, name=None, **kwargs):
     def backends(self, name=None, **kwargs):
         return self._backends
 
+    @deprecate_func(
+        additional_msg="This class has been migrated to the `qiskit_ibm_runtime` package. "
+        "You should migrate your code to "
+        "use `from qiskit_ibm_runtime.fake_provider import FakeProviderExample` "
+        "instead of `from qiskit.providers.fake_provider import FakeProviderExample`.",
+        since="0.46.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         self._backends = [
             FakeAlmaden(),

qiskit/providers/fake_provider/fake_pulse_backend.py

@@ -16,6 +16,7 @@
 
 from qiskit.exceptions import QiskitError
 from qiskit.providers.models import PulseBackendConfiguration, PulseDefaults
+import warnings
 
 from .fake_qasm_backend import FakeQasmBackend
 from .utils.json_decoder import decode_pulse_defaults
@@ -26,6 +27,18 @@ class FakePulseBackend(FakeQasmBackend):
 
     defs_filename = None
 
+    def __init__(self):
+        warnings.warn(
+            message="Device-specific fake backends have been migrated to the `qiskit_ibm_runtime` package. "
+            "These classes are deprecated as of qiskit 0.46.0 and will be removed in qiskit 1.0.0. "
+            "You should migrate your code to use "
+            "`from qiskit_ibm_runtime.fake_provider import FakeExample` "
+            "instead of `from qiskit.providers.fake_provider import FakeExample`.",
+            category=DeprecationWarning,
+            stacklevel=3,
+        )
+        super().__init__()
+
     def defaults(self):
         """Returns a snapshot of device defaults"""
         if not self._defaults:

qiskit/providers/fake_provider/fake_qasm_backend.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2020.
+# (C) Copyright IBM 2020, 2023.
 #
 # 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
@@ -16,6 +16,7 @@
 
 import json
 import os
+import warnings
 
 from qiskit.exceptions import QiskitError
 from qiskit.providers.models import BackendProperties, QasmBackendConfiguration
@@ -36,6 +37,15 @@ class FakeQasmBackend(FakeBackend):
     backend_name = None
 
     def __init__(self):
+        warnings.warn(
+            message="Device-specific fake backends have been migrated to the `qiskit_ibm_runtime` package. "
+            "These classes are deprecated as of qiskit 0.46.0 and will be removed in qiskit 1.0.0. "
+            "You should migrate your code to use "
+            "`from qiskit_ibm_runtime.fake_provider import FakeExample` "
+            "instead of `from qiskit.providers.fake_provider import FakeExample`.",
+            category=DeprecationWarning,
+            stacklevel=3,
+        )
         configuration = self._get_conf_from_json()
         self._defaults = None
         self._properties = None

qiskit/providers/fake_provider/fake_qasm_simulator.py

@@ -15,13 +15,20 @@
 """
 
 from qiskit.providers.models import GateConfig, QasmBackendConfiguration
+from qiskit.utils.deprecation import deprecate_func
 
 from .fake_backend import FakeBackend
 
 
 class FakeQasmSimulator(FakeBackend):
     """A fake simulator backend."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.providers.basic_provider.BasicSimulator` " "class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         configuration = QasmBackendConfiguration(
             backend_name="fake_qasm_simulator",

qiskit/providers/fake_provider/fake_qobj.py

@@ -23,13 +23,20 @@
     QasmQobjExperiment,
     QasmQobjConfig,
 )
+from qiskit.utils.deprecation import deprecate_func
 
 from .fake_qasm_simulator import FakeQasmSimulator
 
 
 class FakeQobj(QasmQobj):
     """A fake `Qobj` instance."""
 
+    @deprecate_func(
+        additional_msg="Use the `qiskit.qobj.QasmQobj` class instead.",
+        since="0.46.0",
+        removal_timeline="Qiskit 1.0",
+        package_name="qiskit",
+    )
     def __init__(self):
         qobj_id = "test_id"
         config = QasmQobjConfig(shots=1024, memory_slots=1)

qiskit/test/base.py

@@ -245,7 +245,6 @@ def setUpClass(cls):
         ]
         for msg in allow_DeprecationWarning_message:
             warnings.filterwarnings("default", category=DeprecationWarning, message=msg)
-
         allow_aer_DeprecationWarning_message = [
             # This warning should be fixed once Qiskit/qiskit-aer#1761 is in a release version of Aer.
             "Setting metadata to None.*",
@@ -257,11 +256,15 @@ def setUpClass(cls):
             "The qiskit.extensions module is deprecated since Qiskit 0.46.0. It will be removed "
             "in the Qiskit 1.0 release.",
         ]
-
         for msg in allow_aer_DeprecationWarning_message:
             warnings.filterwarnings(
                 "default", category=DeprecationWarning, module="qiskit_aer.*", message=msg
             )
+        # Ignore fake backend deprecation warnings to avoid over-crowding the test log
+        ignore_fake_backend_message = r"Device-specific fake backends have been migrated to the `qiskit_ibm_runtime` package.*"
+        warnings.filterwarnings(
+            "ignore", category=DeprecationWarning, message=ignore_fake_backend_message
+        )
 
 
 class FullQiskitTestCase(QiskitTestCase):

releasenotes/notes/deprecate-fake-backends-4dd275cf9a30d41f.yaml

@@ -0,0 +1,50 @@
+---
+deprecations:
+  - |
+    The core functionality of the :mod:`qiskit.providers.fake_provider` module has been migrated to
+    the new ``qiskit_ibm_runtime.fake_provider`` module. For this reason, the following elements in
+    the :mod:`qiskit.providers.fake_provider` have been deprecated as of Qiskit 0.46 and will be
+    removed in Qiskit 1.0:
+
+      * :class:`qiskit.providers.fake_provider.FakeProvider`
+      * :class:`qiskit.providers.fake_provider.FakeProviderForBackendV2`
+      * :class:`qiskit.providers.fake_provider.FakeProviderFactory`
+      * any fake backend contained in :class:`qiskit.providers.fake_provider.backends`
+        (accesible through the provider)
+      * :class:`qiskit.providers.fake_provider.FakeQasmSimulator`
+      * :class:`qiskit.providers.fake_provider.FakeJob`
+      * :class:`qiskit.providers.fake_provider.FakeQobj`
+
+    Migration example to the new fake provider::
+
+      # Legacy path
+      from qiskit.providers.fake_provider import FakeProvider, FakeSherbrooke
+      backend1 = FakeProvider().get_backend("fake_ourense")
+      backend2 = FakeSherbrooke()
+
+      # New path
+      # run "pip install qiskit-ibm-runtime"
+      from qiskit_ibm_runtime.fake_provider import FakeProvider, FakeSherbrooke
+      backend1 = FakeProvider().get_backend("fake_ourense")
+      backend2 = FakeSherbrooke()
+
+    Additionally, the following fake backends designed for special testing purposes have been superseded
+    by the new :class:`.GenericBackendV2` class, and are also deprecated as of Qiskit 0.46:
+
+      * :class:`qiskit.providers.fake_provider.fake_backend_v2.FakeBackendV2`
+      * :class:`qiskit.providers.fake_provider.fake_backend_v2.FakeBackendV2LegacyQubitProps`
+      * :class:`qiskit.providers.fake_provider.fake_backend_v2.FakeBackend5QV2`
+      * :class:`qiskit.providers.fake_provider.fake_backend_v2.FakeBackendSimple`
+
+    Migration example to the new :class:`.GenericBackendV2` class::
+
+      # Legacy path
+      from qiskit.providers.fake_provider import FakeBackend5QV2
+      backend = FakeBackend5QV2()
+
+      # New path
+      from qiskit.providers.fake_provider import GenericBackendV2
+      backend = GenericBackendV2(num_qubits=5)
+      # note that this class will generate 5q backend with generic
+      # properties that serves the same purpose as FakeBackend5QV2
+      # but will generate different results

test/python/algorithms/test_backendv1.py

@@ -31,7 +31,9 @@ class TestBackendV1(QiskitAlgorithmsTestCase):
 
     def setUp(self):
         super().setUp()
-        self._provider = FakeProvider()
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=DeprecationWarning)
+            self._provider = FakeProvider()
         self._qasm = self._provider.get_backend("fake_qasm_simulator")
         self.seed = 50
 

test/python/algorithms/test_backendv2.py

@@ -13,6 +13,7 @@
 """Test Providers that support BackendV2 interface"""
 
 import unittest
+import warnings
 from test.python.algorithms import QiskitAlgorithmsTestCase
 from qiskit import QuantumCircuit
 from qiskit.providers.fake_provider import FakeProvider
@@ -29,8 +30,10 @@ class TestBackendV2(QiskitAlgorithmsTestCase):
 
     def setUp(self):
         super().setUp()
-        self._provider = FakeProvider()
-        self._qasm = FakeBackendSimple()
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=DeprecationWarning)
+            self._provider = FakeProvider()
+            self._qasm = FakeBackendSimple()
         self.seed = 50
 
     def test_vqe_qasm(self):