Remove Aer and imports from qiskit.providers.aer (#11442)

* Remove `Aer` and imports from `qiskit.providers.aer` This removes the `Aer` object and the metapath shenanigans that enabled importing from `qiskit.providers.aer`. All references to `qiskit.providers.aer` in the Terra repository are updated to use `qiskit_aer` instead, which is a drop-in replacement following Aer 0.11. This commit leaves the IBMQ object in place for now, since its removal will affect many other places in the repository and should be handled separately. * Fix randomised-test Aer usage * Remove claim of pulse simulation Co-authored-by: Elena Peña Tapia <[email protected]> --------- Co-authored-by: Elena Peña Tapia <[email protected]> Co-authored-by: Matthew Treinish <[email protected]>
Qiskit · Jan 17, 2024 · bfc6b0d · bfc6b0d
1 parent ed79d42
commit bfc6b0d
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Showing 9 changed files with 44 additions and 171 deletions.
diff --git a/qiskit/__init__.py b/qiskit/__init__.py
@@ -44,16 +44,6 @@
     "qiskit._accelerate.convert_2q_block_matrix"
 ] = qiskit._accelerate.convert_2q_block_matrix
 
-
-# Extend namespace for backwards compat
-from qiskit import namespace
-
-# Add hook to redirect imports from qiskit.providers.aer* to qiskit_aer*
-# this is necessary for backwards compatibility for users when qiskit-aer
-# and qiskit-terra shared the qiskit namespace
-new_meta_path_finder = namespace.QiskitElementImport("qiskit.providers.aer", "qiskit_aer")
-sys.meta_path = [new_meta_path_finder] + sys.meta_path
-
 # qiskit errors operator
 from qiskit.exceptions import QiskitError, MissingOptionalLibraryError
 
@@ -79,54 +69,7 @@
 
 from .version import __version__
 
-
-class AerWrapper:
-    """Lazy loading wrapper for Aer provider."""
-
-    def __init__(self):
-        self.aer = None
-
-    def __bool__(self):
-        if self.aer is None:
-            try:
-                from qiskit.providers import aer
-
-                self.aer = aer.Aer
-                warnings.warn(
-                    "The qiskit.Aer entry point will be deprecated in a future release and "
-                    "subsequently removed. Instead you should use this "
-                    "directly from the root of the qiskit-aer package.",
-                    PendingDeprecationWarning,
-                    stacklevel=2,
-                )
-            except ImportError:
-                return False
-        return True
-
-    def __getattr__(self, attr):
-        if not self.aer:
-            try:
-                from qiskit.providers import aer
-
-                self.aer = aer.Aer
-                warnings.warn(
-                    "The qiskit.Aer entry point will be deprecated in a future release and "
-                    "subsequently removed. Instead you should use this "
-                    "directly from the root of the qiskit-aer package.",
-                    PendingDeprecationWarning,
-                    stacklevel=2,
-                )
-            except ImportError as ex:
-                raise MissingOptionalLibraryError(
-                    "qiskit-aer", "Aer provider", "pip install qiskit-aer"
-                ) from ex
-        return getattr(self.aer, attr)
-
-
-Aer = AerWrapper()
-
 __all__ = [
-    "Aer",
     "AncillaRegister",
     "BasicAer",
     "ClassicalRegister",

diff --git a/qiskit/namespace.py b/qiskit/namespace.py
diff --git a/qiskit/providers/fake_provider/fake_backend.py b/qiskit/providers/fake_provider/fake_backend.py
@@ -118,9 +118,9 @@ def _parse_channels(self, channels):
 
     def _setup_sim(self):
         if _optionals.HAS_AER:
-            from qiskit.providers import aer
+            from qiskit_aer import AerSimulator
 
-            self.sim = aer.AerSimulator()
+            self.sim = AerSimulator()
             if self.target and self._props_dict:
                 noise_model = self._get_noise_model_from_backend_v2()
                 self.sim.set_options(noise_model=noise_model)
@@ -199,9 +199,9 @@ def _default_options(cls):
                 default values set
         """
         if _optionals.HAS_AER:
-            from qiskit.providers import aer
+            from qiskit_aer import AerSimulator
 
-            return aer.AerSimulator._default_options()
+            return AerSimulator._default_options()
         else:
             return basicaer.QasmSimulatorPy._default_options()
 
@@ -348,7 +348,7 @@ def run(self, run_input, **options):
                 "QuantumCircuit, Schedule, or a list of either" % circuits
             )
         if pulse_job:  # pulse job
-            raise QiskitError("Pulse simulation is currently not supported for V2 fake backends.")
+            raise QiskitError("Pulse simulation is currently not supported for fake backends.")
         # circuit job
         if not _optionals.HAS_AER:
             warnings.warn("Aer not found using BasicAer and no noise", RuntimeWarning)
@@ -375,13 +375,13 @@ def _get_noise_model_from_backend_v2(
 
         from qiskit.circuit import Delay
         from qiskit.providers.exceptions import BackendPropertyError
-        from qiskit.providers.aer.noise import NoiseModel
-        from qiskit.providers.aer.noise.device.models import (
+        from qiskit_aer.noise import NoiseModel
+        from qiskit_aer.noise.device.models import (
             _excited_population,
             basic_device_gate_errors,
             basic_device_readout_errors,
         )
-        from qiskit.providers.aer.noise.passes import RelaxationNoisePass
+        from qiskit_aer.noise.passes import RelaxationNoisePass
 
         if self._props_dict is None:
             self._set_props_dict_from_json()
@@ -402,7 +402,7 @@ def _get_noise_model_from_backend_v2(
         with warnings.catch_warnings():
             warnings.filterwarnings(
                 "ignore",
-                module="qiskit.providers.aer.noise.device.models",
+                module="qiskit_aer.noise.device.models",
             )
             gate_errors = basic_device_gate_errors(
                 properties,
@@ -458,10 +458,10 @@ def __init__(self, configuration, time_alive=10):
 
     def _setup_sim(self):
         if _optionals.HAS_AER:
-            from qiskit.providers import aer
-            from qiskit.providers.aer.noise import NoiseModel
+            from qiskit_aer import AerSimulator
+            from qiskit_aer.noise import NoiseModel
 
-            self.sim = aer.AerSimulator()
+            self.sim = AerSimulator()
             if self.properties():
                 noise_model = NoiseModel.from_backend(self)
                 self.sim.set_options(noise_model=noise_model)
@@ -526,9 +526,9 @@ def properties(self):
     @classmethod
     def _default_options(cls):
         if _optionals.HAS_AER:
-            from qiskit.providers import aer
+            from qiskit_aer import QasmSimulator
 
-            return aer.QasmSimulator._default_options()
+            return QasmSimulator._default_options()
         else:
             return basicaer.QasmSimulatorPy._default_options()
 
@@ -552,20 +552,12 @@ def run(self, run_input, **kwargs):
                 "QuantumCircuit, Schedule, or a list of either" % circuits
             )
         if pulse_job:
-            if _optionals.HAS_AER:
-                from qiskit.providers import aer
-                from qiskit.providers.aer.pulse import PulseSystemModel
-
-                system_model = PulseSystemModel.from_backend(self)
-                sim = aer.Aer.get_backend("pulse_simulator")
-                job = sim.run(circuits, system_model=system_model, **kwargs)
-            else:
-                raise QiskitError("Unable to run pulse schedules without qiskit-aer installed")
-        else:
-            if self.sim is None:
-                self._setup_sim()
-            if not _optionals.HAS_AER:
-                warnings.warn("Aer not found using BasicAer and no noise", RuntimeWarning)
-            self.sim._options = self._options
-            job = self.sim.run(circuits, **kwargs)
+            raise QiskitError("Pulse simulation is currently not supported for fake backends.")
+        # circuit job
+        if not _optionals.HAS_AER:
+            warnings.warn("Aer not found using BasicAer and no noise", RuntimeWarning)
+        if self.sim is None:
+            self._setup_sim()
+        self.sim._options = self._options
+        job = self.sim.run(circuits, **kwargs)
         return job
diff --git a/qiskit/test/decorators.py b/qiskit/test/decorators.py
@@ -15,8 +15,8 @@
 
 import functools
 import os
-import unittest
 from typing import Union, Callable, Type, Iterable
+import unittest
 
 from qiskit.utils import wrap_method
 

diff --git a/qiskit/utils/optionals.py b/qiskit/utils/optionals.py
@@ -29,8 +29,8 @@
     :widths: 25 75
 
     * - .. py:data:: HAS_AER
-      - :mod:`Qiskit Aer <qiskit.providers.aer>` provides high-performance simulators for the
-        quantum circuits constructed within Qiskit.
+      - `Qiskit Aer <https://qiskit.org/ecosystem/aer/>` provides high-performance simulators for
+        the quantum circuits constructed within Qiskit.
 
     * - .. py:data:: HAS_IBMQ
       - The :mod:`Qiskit IBMQ Provider <qiskit.providers.ibmq>` is used for accessing IBM Quantum
@@ -224,7 +224,7 @@
 _logger = _logging.getLogger(__name__)
 
 HAS_AER = _LazyImportTester(
-    "qiskit.providers.aer",
+    "qiskit_aer",
     name="Qiskit Aer",
     install="pip install qiskit-aer",
 )

diff --git a/releasenotes/notes/remove-aer-hooks-1144714bbbdd0fe8.yaml b/releasenotes/notes/remove-aer-hooks-1144714bbbdd0fe8.yaml
@@ -0,0 +1,13 @@
+---
+upgrade:
+  - |
+    The object ``qiskit.Aer`` has been removed following its deprecation in Qiskit 0.46.  You can
+    instead use ``qiskit_aer.Aer``, which is a drop-in replacement.
+  - |
+    Importing from ``qiskit.providers.aer`` will no longer work, following its deprecation in Qiskit
+    0.46.  You should instead import from ``qiskit_aer``, which is a drop-in replacement.
+  - |
+    Pulse jobs are no longer supported in fake backends, following the deprecation and removal
+    of the underlying simulation functionality in Qiskit Aer.  For pulse-level simulation, outside
+    the context of circuit objects, consider using a special-purpose library such as
+    `Qiskit Dynamics <https://qiskit.org/ecosystem/dynamics/>`__.
diff --git a/test/python/transpiler/test_sabre_swap.py b/test/python/transpiler/test_sabre_swap.py
@@ -274,7 +274,7 @@ def test_no_infinite_loop(self, method):
         if not optionals.HAS_AER:
             return
 
-        from qiskit import Aer
+        from qiskit_aer import Aer
 
         sim = Aer.get_backend("aer_simulator")
         in_results = sim.run(qc, shots=4096).result().get_counts()

diff --git a/test/randomized/test_transpiler_equivalence.py b/test/randomized/test_transpiler_equivalence.py
@@ -56,7 +56,7 @@
 
 import hypothesis.strategies as st
 
-from qiskit import transpile, Aer, qasm2
+from qiskit import transpile, qasm2
 from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister
 from qiskit.circuit import Measure, Reset, Gate, Barrier
 from qiskit.providers.fake_provider import (
@@ -91,10 +91,11 @@
 )
 from qiskit.test.base import dicts_almost_equal
 
-
 # pylint: disable=wildcard-import,unused-wildcard-import
 from qiskit.circuit.library.standard_gates import *
 
+from qiskit_aer import Aer  # pylint: disable=wrong-import-order
+
 default_profile = "transpiler_equivalence"
 settings.register_profile(
     default_profile,

diff --git a/tools/find_optional_imports.py b/tools/find_optional_imports.py
@@ -29,7 +29,7 @@ def _main():
         "ipywidgets",
         "scipy.stats",
         "matplotlib",
-        "qiskit.providers.aer",
+        "qiskit_aer",
         "qiskit.providers.ibmq",
         "qiskit.ignis",
         "qiskit.aqua",