From e96645dda35c9b6f43f832463212e6cee713d83c Mon Sep 17 00:00:00 2001
From: Will Shanks <willshanks@us.ibm.com>
Date: Tue, 13 Feb 2024 12:18:03 -0500
Subject: [PATCH] Remove `qiskit_ibm_runtime` import from `MockIQBackend` code

The import was only used for subclassing
`qiskit_ibm_runtime.fake_provider.fake_backend.FakeBackendV2`. The code
now subclasses `qiskit.providers.BackendV2` directly.
---
 qiskit_experiments/test/mock_iq_backend.py    | 54 +++++++++----------
 ...thout-qiskit-runtime-20d2bf9edb48312d.yaml |  7 +++
 2 files changed, 33 insertions(+), 28 deletions(-)
 create mode 100644 releasenotes/notes/mock-iq-backend-without-qiskit-runtime-20d2bf9edb48312d.yaml

diff --git a/qiskit_experiments/test/mock_iq_backend.py b/qiskit_experiments/test/mock_iq_backend.py
index 8626af8aac..713a6a1737 100644
--- a/qiskit_experiments/test/mock_iq_backend.py
+++ b/qiskit_experiments/test/mock_iq_backend.py
@@ -11,16 +11,18 @@
 # that they have been altered from the originals.
 
 """A mock IQ backend for testing."""
+import datetime
 from abc import abstractmethod
 from typing import Sequence, List, Tuple, Dict, Union, Any
+
 import numpy as np
 
 from qiskit import QuantumCircuit
 from qiskit.circuit.library import XGate, SXGate
 from qiskit.result import Result
+from qiskit.providers import BackendV2, BackendV2Converter, Provider
 from qiskit.providers.fake_provider import FakeOpenPulse2Q
 from qiskit.qobj.utils import MeasLevel
-from qiskit_ibm_runtime.fake_provider.fake_backend import FakeBackendV2
 
 from qiskit_experiments.exceptions import QiskitError
 from qiskit_experiments.framework import Options
@@ -33,39 +35,35 @@
 )
 
 
-class FakeOpenPulse2QV2(FakeBackendV2):
-    """BackendV2 version of FakeOpenPulse2Q"""
+class FakeOpenPulse2QV2(BackendV2):
+    """BackendV2 conversion of qiskit.providers.fake_provider.FakeOpenPulse2Q"""
+
+    def __init__(
+        self,
+        provider: Provider = None,
+        name: str = None,
+        description: str = None,
+        online_date: datetime.datetime = None,
+        backend_version: str = None,
+        **fields,
+    ):
+        super().__init__(provider, name, description, online_date, backend_version, **fields)
 
-    def __init__(self):
-        # FakeOpenPulse2Q has its data hard-coded rather than in json files. We
-        # prepopulate the dicts so that FakeBackendV2 does not try to load them
-        # from files.
-        #
-        # We have to use a hack to populate _conf_dict
         backend_v1 = FakeOpenPulse2Q()
-        self._conf_dict_real = backend_v1._configuration.to_dict()
-        super().__init__()
-        self._props_dict = backend_v1._properties.to_dict()
-        self._defs_dict = backend_v1._defaults.to_dict()
+        # BackendV2Converter requires the description attribute
+        backend_v1._configuration.description = "A fake test backend with pulse defaults"
+
+        self.backend = BackendV2Converter(backend_v1, add_delay=True)
+        # See commented out defaults() method below
         self._defaults = backend_v1._defaults
 
-        # Workaround a bug in FakeOpenPulse2Q. It defines u1 on qubit 1 in the
-        # cmd_def in the defaults json file but not in the gates in the
-        # properties instance. The code FakeBackendV2 uses to build the Target
-        # assumes these two are consistent.
-        u1_0 = next(g for g in self._props_dict["gates"] if g["gate"] == "u1")
-        self._props_dict["gates"].append(u1_0.copy())
-        self._props_dict["gates"][-1]["qubits"] = [1]
+    @property
+    def max_circuits(self):
+        return 300
 
     @property
-    def _conf_dict(self):
-        # FakeBackendV2 sets this in __init__. As a hack, we use this property
-        # to prevent it from overriding our values.
-        return self._conf_dict_real
-
-    @_conf_dict.setter
-    def _conf_dict(self, value):
-        pass
+    def target(self):
+        return self.backend.target
 
     # This method is not defined in the base class as we would like to avoid
     # relying on it as much as necessary. Individual tests should add it when
diff --git a/releasenotes/notes/mock-iq-backend-without-qiskit-runtime-20d2bf9edb48312d.yaml b/releasenotes/notes/mock-iq-backend-without-qiskit-runtime-20d2bf9edb48312d.yaml
new file mode 100644
index 0000000000..71eadd9fb0
--- /dev/null
+++ b/releasenotes/notes/mock-iq-backend-without-qiskit-runtime-20d2bf9edb48312d.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    :class:`.MockIQBackend` was refactored so that it does not import
+    ``qiskit_ibm_runtime`` since
+    :external+qiskit_ibm_runtime:doc:`qiskit-ibm-runtime <index>` is not a
+    required dependency of Qiskit Experiments.