Fix handling of simulator backends in BackendV2Converter (backport #9630)

qiskit/providers/backend_compat.py

@@ -138,9 +138,7 @@ def convert_to_target(
     for op in combined_global_ops:
         if op not in target:
             if op in name_mapping:
-                target.add_instruction(
-                    name_mapping[op], {(bit,): None for bit in range(target.num_qubits)}
-                )
+                target.add_instruction(name_mapping[op], name=op)
             else:
                 raise QiskitError(
                     f"Operation name '{op}' does not have a known mapping. Use "
@@ -220,7 +218,7 @@ def __init__(
             provider=backend.provider,
             name=backend.name(),
             description=self._config.description,
-            online_date=self._config.online_date,
+            online_date=getattr(self._config, "online_date", None),
             backend_version=self._config.backend_version,
         )
         self._options = self._backend._options

releasenotes/notes/fix-backendv2-converter-simulator-e8f150d1fd6861fe.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixed an issue with the :class:`~.BackendV2Converter` class when wrapping
+    a :class:`~.BackendV1` based simulator which would error if either
+    the ``online_date`` field in the :class:`~.BackendConfiguration` for the
+    simulator was not present or if the simulator backend supports ideal
+    implementations of gates that involve more than 1 qubit.
+    Fixed `#9562 <https://github.com/Qiskit/qiskit-terra/issues/9562>`__

test/python/providers/test_fake_backends.py

@@ -14,6 +14,7 @@
 # pylint: disable=missing-module-docstring
 
 import operator
+import unittest
 
 from test import combine
 from ddt import ddt, data
@@ -34,6 +35,30 @@
 from qiskit.providers.backend_compat import BackendV2Converter
 from qiskit.providers.backend import BackendV2
 from qiskit.utils import optionals
+from qiskit.circuit.library import (
+    SXGate,
+    MCPhaseGate,
+    MCXGate,
+    RZGate,
+    RXGate,
+    U2Gate,
+    U1Gate,
+    U3Gate,
+    YGate,
+    ZGate,
+    PauliGate,
+    SwapGate,
+    RGate,
+    MCXGrayCode,
+    RYGate,
+)
+from qiskit.circuit import ControlledGate, Parameter
+from qiskit.quantum_info.operators.channel.quantum_channel import QuantumChannel
+from qiskit.quantum_info.operators.channel.kraus import Kraus
+from qiskit.quantum_info.operators.channel import SuperOp
+from qiskit.extensions import Initialize, UnitaryGate
+from qiskit.extensions.quantum_initializer import DiagonalGate, UCGate
+from qiskit.circuit.controlflow import IfElseOp, WhileLoopOp, ForLoopOp
 
 FAKE_PROVIDER_FOR_BACKEND_V2 = FakeProviderForBackendV2()
 FAKE_PROVIDER = FakeProvider()
@@ -193,3 +218,243 @@ def test_converter_delay_circuit(self):
         qc.measure_all()
         res = transpile(qc, backend_v2)
         self.assertIn("delay", res.count_ops())
+
+    @unittest.skipUnless(optionals.HAS_AER, "Aer required for this test")
+    def test_converter_simulator(self):
+        class MCSXGate(ControlledGate):
+            def __init__(self, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcsx",
+                    1 + num_ctrl_qubits,
+                    [],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=SXGate(),
+                )
+
+        class MCYGate(ControlledGate):
+            def __init__(self, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcy",
+                    1 + num_ctrl_qubits,
+                    [],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=YGate(),
+                )
+
+        class MCZGate(ControlledGate):
+            def __init__(self, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcz",
+                    1 + num_ctrl_qubits,
+                    [],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=ZGate(),
+                )
+
+        class MCRXGate(ControlledGate):
+            def __init__(self, theta, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcrx",
+                    1 + num_ctrl_qubits,
+                    [theta],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=RXGate(theta),
+                )
+
+        class MCRYGate(ControlledGate):
+            def __init__(self, theta, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcry",
+                    1 + num_ctrl_qubits,
+                    [theta],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=RYGate(theta),
+                )
+
+        class MCRZGate(ControlledGate):
+            def __init__(self, theta, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcrz",
+                    1 + num_ctrl_qubits,
+                    [theta],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=RZGate(theta),
+                )
+
+        class MCRGate(ControlledGate):
+            def __init__(self, theta, phi, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcr",
+                    1 + num_ctrl_qubits,
+                    [theta, phi],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=RGate(theta, phi),
+                )
+
+        class MCU1Gate(ControlledGate):
+            def __init__(self, theta, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcu1",
+                    1 + num_ctrl_qubits,
+                    [theta],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=U1Gate(theta),
+                )
+
+        class MCU2Gate(ControlledGate):
+            def __init__(self, theta, lam, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcu2",
+                    1 + num_ctrl_qubits,
+                    [theta, lam],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=U2Gate(theta, lam),
+                )
+
+        class MCU3Gate(ControlledGate):
+            def __init__(self, theta, lam, phi, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcu3",
+                    1 + num_ctrl_qubits,
+                    [theta, phi, lam],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=U3Gate(theta, phi, lam),
+                )
+
+        class MCUGate(ControlledGate):
+            def __init__(self, theta, lam, phi, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcu",
+                    1 + num_ctrl_qubits,
+                    [theta, phi, lam],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=U3Gate(theta, phi, lam),
+                )
+
+        class MCSwapGate(ControlledGate):
+            def __init__(self, num_ctrl_qubits, ctrl_state=None):
+                super().__init__(
+                    "mcswap",
+                    2 + num_ctrl_qubits,
+                    [],
+                    None,
+                    num_ctrl_qubits,
+                    ctrl_state=ctrl_state,
+                    base_gate=SwapGate(),
+                )
+
+        from qiskit_aer import AerSimulator
+        from qiskit_aer.library import (
+            SaveExpectationValue,
+            SaveAmplitudes,
+            SaveStatevectorDict,
+            SaveSuperOp,
+            SaveClifford,
+            SaveMatrixProductState,
+            SaveDensityMatrix,
+            SaveProbabilities,
+            SaveStatevector,
+            SetDensityMatrix,
+            SetUnitary,
+            SaveState,
+            SetMatrixProductState,
+            SaveUnitary,
+            SetSuperOp,
+            SaveExpectationValueVariance,
+            SaveStabilizer,
+            SetStatevector,
+            SetStabilizer,
+            SaveAmplitudesSquared,
+            SaveProbabilitiesDict,
+        )
+        from qiskit_aer.noise.errors import ReadoutError
+        from qiskit_aer.noise.noise_model import QuantumErrorLocation
+
+        sim = AerSimulator()
+        phi = Parameter("phi")
+        lam = Parameter("lam")
+        backend = BackendV2Converter(
+            sim,
+            name_mapping={
+                "mcsx": MCSXGate,
+                "mcp": MCPhaseGate,
+                "mcphase": MCPhaseGate,
+                "quantum_channel": QuantumChannel,
+                "initialize": Initialize,
+                "save_expval": SaveExpectationValue,
+                "diagonal": DiagonalGate,
+                "save_amplitudes": SaveAmplitudes,
+                "roerror": ReadoutError,
+                "mcrx": MCRXGate,
+                "kraus": Kraus,
+                "save_statevector_dict": SaveStatevectorDict,
+                "mcx": MCXGate,
+                "mcu1": MCU1Gate,
+                "mcu2": MCU2Gate,
+                "mcu3": MCU3Gate,
+                "save_superop": SaveSuperOp,
+                "multiplexer": UCGate,
+                "mcy": MCYGate,
+                "superop": SuperOp,
+                "save_clifford": SaveClifford,
+                "save_matrix_product_state": SaveMatrixProductState,
+                "save_density_matrix": SaveDensityMatrix,
+                "save_probabilities": SaveProbabilities,
+                "if_else": IfElseOp,
+                "while_loop": WhileLoopOp,
+                "for_loop": ForLoopOp,
+                "save_statevector": SaveStatevector,
+                "mcu": MCUGate,
+                "set_density_matrix": SetDensityMatrix,
+                "qerror_loc": QuantumErrorLocation,
+                "unitary": UnitaryGate,
+                "mcz": MCZGate,
+                "pauli": PauliGate,
+                "set_unitary": SetUnitary,
+                "save_state": SaveState,
+                "mcswap": MCSwapGate,
+                "set_matrix_product_state": SetMatrixProductState,
+                "save_unitary": SaveUnitary,
+                "mcr": MCRGate,
+                "mcx_gray": MCXGrayCode,
+                "mcrz": MCRZGate,
+                "set_superop": SetSuperOp,
+                "save_expval_var": SaveExpectationValueVariance,
+                "save_stabilizer": SaveStabilizer,
+                "set_statevector": SetStatevector,
+                "mcry": MCRYGate,
+                "set_stabilizer": SetStabilizer,
+                "save_amplitudes_sq": SaveAmplitudesSquared,
+                "save_probabilities_dict": SaveProbabilitiesDict,
+                "cu2": U2Gate(phi, lam).control(),
+            },
+        )
+        self.assertIsInstance(backend, BackendV2)
+        res = transpile(self.circuit, backend)
+        job = backend.run(res)
+        result = job.result()
+        counts = result.get_counts()
+        max_count = max(counts.items(), key=operator.itemgetter(1))[0]
+        self.assertEqual(max_count, "11")