Fix qpy for multiple controlled parametrized gates (#10758) (#10795)

* Add exception for controlled gate

* Add reno

(cherry picked from commit ebb1197)

Co-authored-by: Elena Peña Tapia <57907331+ElePT@users.noreply.github.com>

qiskit/qpy/binary_io/circuits.py

@@ -540,14 +540,18 @@ def _write_instruction(file_obj, instruction, custom_operations, index_map):
         )
         or gate_class_name == "Gate"
         or gate_class_name == "Instruction"
-        or gate_class_name == "ControlledGate"
         or isinstance(instruction.operation, library.BlueprintCircuit)
     ):
         if instruction.operation.name not in custom_operations:
             custom_operations[instruction.operation.name] = instruction.operation
             custom_operations_list.append(instruction.operation.name)
         gate_class_name = instruction.operation.name
 
+    elif gate_class_name == "ControlledGate":
+        gate_class_name = instruction.operation.name + "_" + str(uuid.uuid4())
+        custom_operations[gate_class_name] = instruction.operation
+        custom_operations_list.append(gate_class_name)
+
     elif isinstance(instruction.operation, library.PauliEvolutionGate):
         gate_class_name = r"###PauliEvolutionGate_" + str(uuid.uuid4())
         custom_operations[gate_class_name] = instruction.operation

releasenotes/notes/fix-qpy-repeated-controlled-gates-e19fc4ee65a22756.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixed a bug in QPY serialization (:mod:`qiskit.qpy`) where if a circuit contained
+    multiple instances of parametrized controlled gates of the same class (not custom),
+    the parameter values from the first instance were used to build the gate definitions
+    of subsequent instances. The gates were rendered correctly despite this bug because
+    the correct parameter values were stored, but not used to build the gates. Fixed
+    `#10735 <https://github.com/Qiskit/qiskit-terra/issues/10735>`__.

test/python/circuit/test_circuit_load_from_qpy.py

@@ -29,6 +29,7 @@
 from qiskit.circuit.gate import Gate
 from qiskit.circuit.library import (
     XGate,
+    RYGate,
     QFT,
     QAOAAnsatz,
     PauliEvolutionGate,
@@ -1310,6 +1311,25 @@ def _define(self) -> None:
         self.assertEqual(qc.decompose(), new_circ.decompose())
         self.assertDeprecatedBitProperties(qc, new_circ)
 
+    def test_multiple_controlled_gates(self):
+        """Test multiple controlled gates with same name but different
+        parameter values.
+
+        Reproduce from: https://github.com/Qiskit/qiskit-terra/issues/10735
+        """
+
+        qc = QuantumCircuit(3)
+        for i in range(3):
+            c2ry = RYGate(i + 1).control(2)
+            qc.append(c2ry, [i % 3, (i + 1) % 3, (i + 2) % 3])
+        qpy_file = io.BytesIO()
+        dump(qc, qpy_file)
+        qpy_file.seek(0)
+        new_circ = load(qpy_file)[0]
+        self.assertEqual(qc, new_circ)
+        self.assertEqual(qc.decompose(), new_circ.decompose())
+        self.assertDeprecatedBitProperties(qc, new_circ)
+
     def test_load_with_loose_bits(self):
         """Test that loading from a circuit with loose bits works."""
         qc = QuantumCircuit([Qubit(), Qubit(), Clbit()])