BackendEstimator support BackendV2 without coupling_map

qiskit/primitives/backend_estimator.py

@@ -15,7 +15,6 @@
 
 from __future__ import annotations
 
-import copy
 import typing
 from collections.abc import Sequence
 from itertools import accumulate
@@ -29,7 +28,14 @@
 from qiskit.quantum_info import Pauli, PauliList
 from qiskit.quantum_info.operators.base_operator import BaseOperator
 from qiskit.result import Counts, Result
-from qiskit.transpiler import PassManager
+from qiskit.transpiler import CouplingMap, PassManager
+from qiskit.transpiler.passes import (
+    ApplyLayout,
+    EnlargeWithAncilla,
+    FullAncillaAllocation,
+    Optimize1qGatesDecomposition,
+    SetLayout,
+)
 
 from .base import BaseEstimator, EstimatorResult
 from .primitive_job import PrimitiveJob
@@ -210,9 +216,8 @@ def _transpile(self):
                     perm_pattern = list(range(transpiled_circuit.num_qubits))
 
             # 2. transpile diff circuits
-            transpile_opts = copy.copy(self.transpile_options)
-            transpile_opts.update_options(initial_layout=perm_pattern)
-            diff_circuits = transpile(diff_circuits, self.backend, **transpile_opts.__dict__)
+            passmanager = _passmanager_for_measurement_circuits(perm_pattern, self.backend)
+            diff_circuits = passmanager.run(diff_circuits)
             # 3. combine
             transpiled_circuits = []
             for diff_circuit in diff_circuits:
@@ -344,7 +349,7 @@ def _preprocessing(self) -> list[tuple[QuantumCircuit, list[QuantumCircuit]]]:
                     }
                     diff_circuits.append(meas_circuit)
             else:
-                for basis, obs in zip(observable.paulis, observable):  # type: ignore
+                for basis, obs in zip(observable.paulis, observable):
                     meas_circuit, indices = self._measurement_circuit(circuit.num_qubits, basis)
                     paulis = PauliList.from_symplectic(
                         obs.paulis.z[:, indices],
@@ -456,3 +461,22 @@ def _pauli_expval_with_variance(counts: Counts, paulis: PauliList) -> tuple[np.n
     # Compute variance
     variances = 1 - expvals**2
     return expvals, variances
+
+
+def _passmanager_for_measurement_circuits(layout, backend) -> PassManager:
+    passmanager = PassManager([SetLayout(layout)])
+    if isinstance(backend, BackendV2):
+        opt1q = Optimize1qGatesDecomposition(target=backend.target)
+    else:
+        opt1q = Optimize1qGatesDecomposition(basis=backend.configuration().basis_gates)
+    passmanager.append(opt1q)
+    if isinstance(backend, BackendV2) and isinstance(backend.coupling_map, CouplingMap):
+        coupling_map = backend.coupling_map
+        passmanager.append(FullAncillaAllocation(coupling_map))
+        passmanager.append(EnlargeWithAncilla())
+    elif isinstance(backend, BackendV1) and backend.configuration().coupling_map is not None:
+        coupling_map = CouplingMap(backend.configuration().coupling_map)
+        passmanager.append(FullAncillaAllocation(coupling_map))
+        passmanager.append(EnlargeWithAncilla())
+    passmanager.append(ApplyLayout())
+    return passmanager

releasenotes/notes/backend-estimator-v2-support-a698353aeeb5236c.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed a bug where :class:`.primitives.BackendEstimator` cannot be used with the
+    :class:`.providers.BackendV2` that does not have coupling_map.

test/python/primitives/test_backend_estimator.py

@@ -25,12 +25,13 @@
 from qiskit.primitives import BackendEstimator, EstimatorResult
 from qiskit.providers import JobV1
 from qiskit.providers.fake_provider import FakeNairobi, FakeNairobiV2
+from qiskit.providers.fake_provider.fake_backend_v2 import FakeBackendSimple
 from qiskit.quantum_info import SparsePauliOp
 from qiskit.test import QiskitTestCase
 from qiskit.transpiler import PassManager
 from qiskit.utils import optionals
 
-BACKENDS = [FakeNairobi(), FakeNairobiV2()]
+BACKENDS = [FakeNairobi(), FakeNairobiV2(), FakeBackendSimple()]
 
 
 @ddt
@@ -359,7 +360,7 @@ def test_layout(self, backend):
             estimator = BackendEstimator(backend)
             estimator.set_transpile_options(seed_transpiler=15)
             value = estimator.run(qc, op, shots=10000).result().values[0]
-            if optionals.HAS_AER:
+            if optionals.HAS_AER and not isinstance(backend, FakeBackendSimple):
                 self.assertEqual(value, -0.916)
             else:
                 self.assertEqual(value, -1)
@@ -374,7 +375,7 @@ def test_layout(self, backend):
             estimator = BackendEstimator(backend)
             estimator.set_transpile_options(initial_layout=[0, 1, 2], seed_transpiler=15)
             value = estimator.run(qc, op, shots=10000).result().values[0]
-            if optionals.HAS_AER:
+            if optionals.HAS_AER and not isinstance(backend, FakeBackendSimple):
                 self.assertEqual(value, -0.8902)
             else:
                 self.assertEqual(value, -1)