Handle control flow instructions in Target generation (Qiskit#1443)

* Handle control flow instructions in Target generation

This commit updates the convert_to_target() function that is used to
convert the API response objects used to describe a backend and generate
a Qiskit Target object from that to properly handle control flow
instructions. The supported control flow instructions are listed in the
`supported_instructions` field of the configuration payload. [1] This
commit updates the logic to look for the presence of known control flow
instruction names in that field and add them as appropriate to the
target as global variadic instructions to indicate to Qiskit's
transpiler and other Target object users that the backend supports the
instructions.

[1] https://github.com/Qiskit/ibm-quantum-schemas/blob/0231221082ec722cc31db09c0b41a25f441ac338/schemas/backend_configuration_schema.json#L165-L170

* Add release note

---------

Co-authored-by: Jessie Yu <[email protected]>

qiskit_ibm_runtime/utils/backend_converter.py

@@ -25,6 +25,8 @@
     ECRGate,
     CZGate,
 )
+from qiskit.circuit.controlflow import CONTROL_FLOW_OP_NAMES
+from qiskit.circuit import IfElseOp, WhileLoopOp, ForLoopOp, SwitchCaseOp
 from qiskit.circuit.parameter import Parameter
 from qiskit.circuit.delay import Delay
 from qiskit.circuit.gate import Gate
@@ -56,6 +58,10 @@ def convert_to_target(
         "reset": Reset(),
         "ecr": ECRGate(),
         "cz": CZGate(),
+        "if_else": IfElseOp,
+        "while_loop": WhileLoopOp,
+        "for_loop": ForLoopOp,
+        "switch_case": SwitchCaseOp,
     }
     custom_gates = {}
     target = None
@@ -128,6 +134,10 @@ def convert_to_target(
         target.min_length = configuration.timing_constraints.get("min_length")
         target.pulse_alignment = configuration.timing_constraints.get("pulse_alignment")
         target.acquire_alignment = configuration.timing_constraints.get("acquire_alignment")
+    supported_instructions = set(getattr(configuration, "supported_instructions", []))
+    control_flow_ops = CONTROL_FLOW_OP_NAMES.intersection(supported_instructions)
+    for op in control_flow_ops:
+        target.add_instruction(name_mapping[op], name=op)
     # If pulse defaults exists use that as the source of truth
     if defaults is not None:
         faulty_qubits = set()

releasenotes/notes/fix-control-flow-d5a61dd5647acb42.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixed an issue with the :attr:`.IBMBackend.target` where it would
+    incorrectly exclude supported control flow operations (:class:`.IfElseOp`,
+    :class:`.WhileLoop`, etc.) if a given backend supported them.

test/unit/test_backend.py

@@ -16,11 +16,18 @@
 import warnings
 
 from qiskit import transpile, qasm3, QuantumCircuit
-from qiskit.providers.models import BackendStatus
+from qiskit.circuit import IfElseOp
+from qiskit.providers.models import (
+    BackendStatus,
+    BackendConfiguration,
+    BackendProperties,
+    PulseDefaults,
+)
 
 from qiskit_ibm_runtime.exceptions import IBMBackendValueError
-from qiskit_ibm_runtime.fake_provider import FakeManila
+from qiskit_ibm_runtime.fake_provider import FakeManila, FakeSherbrooke
 from qiskit_ibm_runtime.ibm_backend import IBMBackend
+from qiskit_ibm_runtime.utils.backend_converter import convert_to_target
 
 from ..ibm_test_case import IBMTestCase
 from ..utils import (
@@ -305,3 +312,17 @@ def test_too_many_circuits(self):
             f"Number of circuits, {max_circs+1} exceeds the maximum for this backend, {max_circs}",
             str(err.exception),
         )
+
+    def test_control_flow_converter(self):
+        """Test that control flow instructions are properly added to the target."""
+        backend = FakeSherbrooke()
+        backend._get_conf_dict_from_json()
+        backend._set_props_dict_from_json()
+        backend._set_defs_dict_from_json()
+        target = convert_to_target(
+            BackendConfiguration.from_dict(backend._conf_dict),
+            BackendProperties.from_dict(backend._props_dict),
+            PulseDefaults.from_dict(backend._defs_dict),
+        )
+        self.assertTrue(target.instruction_supported("if_else", ()))
+        self.assertTrue(target.instruction_supported(operation_class=IfElseOp))