Add new get_control_flow_name_mapping function (Qiskit#13472)

* Add new get_control_flow_name_mapping function, replace use in generate_preset_pass_manager and add reno.

* Document function

* Reword documentation

* Use get_control_flow_name_mapping in convert_to_target

qiskit/circuit/__init__.py

@@ -698,6 +698,11 @@
 
     Set of the instruction names of Qiskit's known control-flow operations.
 
+The :func:`.get_control_flow_name_mapping` function allows to access the control-flow operation
+classes associated to each name.
+
+.. autofunction:: get_control_flow_name_mapping
+
 These control-flow operations (:class:`IfElseOp`, :class:`WhileLoopOp`,
 :class:`SwitchCaseOp` and :class:`ForLoopOp`) all have specific state that defines the branching
 conditions and strategies, but contain all the different subcircuit blocks that might be entered in
@@ -1313,6 +1318,7 @@ def __array__(self, dtype=None, copy=None):
     BreakLoopOp,
     ContinueLoopOp,
     CONTROL_FLOW_OP_NAMES,
+    get_control_flow_name_mapping,
 )
 
 from .annotated_operation import AnnotatedOperation, InverseModifier, ControlModifier, PowerModifier

qiskit/circuit/controlflow/__init__.py

@@ -26,3 +26,32 @@
 
 CONTROL_FLOW_OP_NAMES = frozenset(("for_loop", "while_loop", "if_else", "switch_case"))
 """Set of the instruction names of Qiskit's known control-flow operations."""
+
+
+def get_control_flow_name_mapping():
+    """Return a dictionary mapping the names of control-flow operations
+    to their corresponding classes."
+
+    Examples:
+
+        .. code-block:: python
+
+            from qiskit.circuit import get_control_flow_name_mapping
+
+            ctrl_flow_name_map = get_control_flow_name_mapping()
+            if_else_object = ctrl_flow_name_map["if_else"]
+
+            print(if_else_object)
+
+        .. code-block:: text
+
+            <class 'qiskit.circuit.controlflow.if_else.IfElseOp'>
+    """
+
+    name_mapping = {
+        "if_else": IfElseOp,
+        "while_loop": WhileLoopOp,
+        "for_loop": ForLoopOp,
+        "switch_case": SwitchCaseOp,
+    }
+    return name_mapping

qiskit/providers/backend_compat.py

@@ -21,7 +21,7 @@
 from qiskit.providers.backend import QubitProperties
 from qiskit.providers.models.backendconfiguration import BackendConfiguration
 from qiskit.providers.models.backendproperties import BackendProperties
-from qiskit.circuit.controlflow import CONTROL_FLOW_OP_NAMES
+from qiskit.circuit.controlflow import CONTROL_FLOW_OP_NAMES, get_control_flow_name_mapping
 from qiskit.providers.models.pulsedefaults import PulseDefaults
 from qiskit.providers.options import Options
 from qiskit.providers.exceptions import BackendPropertyError
@@ -79,7 +79,6 @@ def _convert_to_target(
         Target,
         InstructionProperties,
     )
-    from qiskit.circuit.controlflow import ForLoopOp, IfElseOp, SwitchCaseOp, WhileLoopOp
     from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
     from qiskit.circuit.parameter import Parameter
     from qiskit.circuit.gate import Gate
@@ -91,12 +90,7 @@ def _convert_to_target(
     if custom_name_mapping:
         qiskit_inst_mapping.update(custom_name_mapping)
 
-    qiskit_control_flow_mapping = {
-        "if_else": IfElseOp,
-        "while_loop": WhileLoopOp,
-        "for_loop": ForLoopOp,
-        "switch_case": SwitchCaseOp,
-    }
+    qiskit_control_flow_mapping = get_control_flow_name_mapping()
 
     in_data = {"num_qubits": configuration.num_qubits}
 

qiskit/transpiler/preset_passmanagers/generate_preset_pass_manager.py

@@ -17,13 +17,7 @@
 import copy
 import warnings
 
-from qiskit.circuit.controlflow import (
-    CONTROL_FLOW_OP_NAMES,
-    IfElseOp,
-    WhileLoopOp,
-    ForLoopOp,
-    SwitchCaseOp,
-)
+from qiskit.circuit.controlflow import CONTROL_FLOW_OP_NAMES, get_control_flow_name_mapping
 from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
 from qiskit.circuit.quantumregister import Qubit
 from qiskit.providers.backend import Backend
@@ -456,12 +450,7 @@ def _parse_basis_gates(basis_gates, backend, inst_map, skip_target):
     standard_gates = get_standard_gate_name_mapping()
     # Add control flow gates by default to basis set and name mapping
     default_gates = {"measure", "delay", "reset"}.union(CONTROL_FLOW_OP_NAMES)
-    name_mapping = {
-        "if_else": IfElseOp,
-        "while_loop": WhileLoopOp,
-        "for_loop": ForLoopOp,
-        "switch_case": SwitchCaseOp,
-    }
+    name_mapping = get_control_flow_name_mapping()
     try:
         instructions = set(basis_gates)
         for name in default_gates:

releasenotes/notes/add-ctrl-flow-name-mapping-21842a23726e6e77.yaml

@@ -0,0 +1,19 @@
+---
+features_circuits:
+  - |
+    Added a new :func:`.get_control_flow_name_mapping` convenience function that returns a 
+    mapping of Qiskit's control-flow operation names to their corresponding class. 
+    Example usage:
+
+    .. code-block:: python
+
+        from qiskit.circuit import get_control_flow_name_mapping
+
+        ctrl_flow_name_map = get_control_flow_name_mapping()
+        if_else_object = ctrl_flow_name_map["if_else"]
+
+        print(if_else_object)
+
+    .. code-block:: text
+
+        <class 'qiskit.circuit.controlflow.if_else.IfElseOp'>