Primitives support the dynamic circuits with control flow

qiskit/primitives/utils.py

@@ -14,6 +14,8 @@
 """
 from __future__ import annotations
 
+from collections.abc import Iterable
+
 import numpy as np
 
 from qiskit.circuit import Instruction, ParameterExpression, QuantumCircuit
@@ -125,6 +127,16 @@ def _bits_key(bits: tuple[Bit, ...], circuit: QuantumCircuit) -> tuple:
     )
 
 
+def _format_params(param):
+    if isinstance(param, np.ndarray):
+        return param.data.tobytes()
+    elif isinstance(param, QuantumCircuit):
+        return _circuit_key(param)
+    elif isinstance(param, Iterable):
+        return tuple(param)
+    return param
+
+
 def _circuit_key(circuit: QuantumCircuit, functional: bool = True) -> tuple:
     """Private key function for QuantumCircuit.
 
@@ -147,10 +159,7 @@ def _circuit_key(circuit: QuantumCircuit, functional: bool = True) -> tuple:
                 _bits_key(data.qubits, circuit),  # qubits
                 _bits_key(data.clbits, circuit),  # clbits
                 data.operation.name,  # operation.name
-                tuple(
-                    param.data.tobytes() if isinstance(param, np.ndarray) else param
-                    for param in data.operation.params
-                ),  # operation.params
+                tuple(_format_params(param) for param in data.operation.params),  # operation.params
             )
             for data in circuit.data
         ),

releasenotes/notes/circuit-key-supports-controlflow-a956ebd2fcebaece.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Primitives support the dynamic circuits with control flow.
+    If backend supports it, users can run the circuits using :class:`~BackendSampler`
+    and :class:`~BackendEstimator`.

test/python/primitives/test_sampler.py

@@ -12,6 +12,7 @@
 
 """Tests for Sampler."""
 
+import json
 import unittest
 from test import combine
 
@@ -783,6 +784,19 @@ def test_circuit_with_unitary(self):
         sampler_result = sampler.run([circuit]).result()
         self.assertDictAlmostEqual(sampler_result.quasi_dists[0], {0: 1, 1: 0})
 
+    def test_circuit_key_controlflow(self):
+        """Test for a circuit with control flow."""
+        qc = QuantumCircuit(2, 1)
+
+        with qc.for_loop(range(5)):
+            qc.h(0)
+            qc.cx(0, 1)
+            qc.measure(0, 0)
+            qc.break_loop().c_if(0, True)
+
+        self.assertIsInstance(hash(_circuit_key(qc)), int)
+        self.assertIsInstance(json.dumps(_circuit_key(qc)), str)
+
 
 if __name__ == "__main__":
     unittest.main()