Issue 6633: Update _parameter_table after circuit assignment

qiskit/circuit/parametertable.py

@@ -17,6 +17,7 @@
 from collections.abc import MutableMapping, MappingView
 
 from .instruction import Instruction
+from .parameter import Parameter
 
 
 class ParameterTable(MutableMapping):
@@ -52,6 +53,13 @@ def __setitem__(self, parameter, instr_params):
         self._keys.add(parameter)
         self._names.add(parameter.name)
 
+    def delete_element(self, instruction: Instruction):
+        for param_index, param in enumerate(instruction.params):
+            if isinstance(param, Parameter):
+                for idx, spec in enumerate(self._table[param]):
+                    if spec[0] is instruction and spec[1] == param_index:
+                        self._table[param].pop(idx)
+
     def get_keys(self):
         """Return a set of all keys in the parameter table
 

qiskit/circuit/quantumcircuitdata.py

@@ -54,6 +54,10 @@ def __setitem__(self, key, value):
         self._circuit._check_qargs(qargs)
         self._circuit._check_cargs(cargs)
 
+        if isinstance(self._circuit._data[key], tuple):
+            old_instruction = self._circuit._data[key][0]
+            self._circuit._parameter_table.delete_element(old_instruction)
+
         self._circuit._data[key] = (instruction, qargs, cargs)
 
         self._circuit._update_parameter_table(instruction)

releasenotes/notes/parameter-table-updated-after-circuit-assignment-61bae00b33f8cf40.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed a bug when ``QuantumCircuit._parameter_table`` is inconsistent with
+    ``QuantumCircuit.data`` after a circuit assignment.
+    In __setitem__ of QuantumCiruitData, for each new entry, the old element 
+    is removed and the new element is added properly.

test/python/circuit/test_circuit_data.py

@@ -13,7 +13,7 @@
 """Test operations on circuit.data."""
 
 from qiskit.circuit import QuantumCircuit, QuantumRegister, Parameter
-from qiskit.circuit.library import HGate, XGate, CXGate, RXGate
+from qiskit.circuit.library import HGate, XGate, CXGate, RXGate, UGate
 
 from qiskit.test import QiskitTestCase
 from qiskit.circuit.exceptions import CircuitError
@@ -425,3 +425,68 @@ def test_param_gate_instance(self):
         qc0_instance = qc0._parameter_table[b][0][0]
         qc1_instance = qc1._parameter_table[a][0][0]
         self.assertNotEqual(qc0_instance, qc1_instance)
+
+    def test_parameter_table_is_updated(self):
+        """
+        Verify that qc._parameter_table is consistent with qc.data when qc.data is updated with __setitem__ in quantumcircuitdata.py
+
+         - Case1-1. Add an instruction with a parameter that was not previously in ParameterTable.
+         - Case1-2. Add an instrcution with a parameter that was in ParameterTable.
+
+         - Case2-1. Replace an instruction with a parameter by other instruction with the same parameter.
+         - Case2-2. Replace an instruction with a parameter by other instruction with a different parameter.
+         - Case2-3. Replace an instruction with a parameter by other instruction with no parameter.
+
+         - Case3-1. Add an instruction with multiple parameter
+         - Case3-2. Replace an instruction with multiple parameter by other instruction
+
+        """
+        qr = QuantumRegister(3, "q")
+        qc = QuantumCircuit(qr)
+        qc_case1 = qc.copy()
+        qc_case2 = qc.copy()
+        qc_case3 = qc.copy()
+
+        # Case1-1, 1-2
+        param1 = Parameter("param1")
+        qc.rx(param1, 0)  # Case1-1
+        qc.rx(param1, 0)  # Case1-2
+        qc.rx(param1, 0)
+
+        # Create an expected ParaemterTable for Case1-1, 1-2
+        qc_case1._parameter_table[param1] = [(qc.data[0][0], 0)]
+        qc_case1._parameter_table[param1].append((qc.data[1][0], 0))
+        qc_case1._parameter_table[param1].append((qc.data[2][0], 0))
+
+        # Assertion for Case1-1, 1-2
+        self.assertEqual(qc._parameter_table, qc_case1._parameter_table)
+
+        # Case2-1, 2-2, 2-3
+        param2 = Parameter("param2")
+        qc.data[0] = (RXGate(param1), [qr[0]], [])  # Case2-1
+        qc.data[1] = (RXGate(param2), [qr[0]], [])  # Case2-2
+        qc.data[2] = (HGate(), [qr[0]], [])  # Case2-3
+
+        # Create an expected ParaemterTable for Case2-1, 2-2, 2-3
+        qc_case2._parameter_table[param1] = [(qc.data[0][0], 0)]
+        qc_case2._parameter_table[param2] = [(qc.data[1][0], 0)]
+
+        # Assertion for Case2-1, 2-2, 2-3
+        self.assertEqual(qc._parameter_table, qc_case2._parameter_table)
+
+        # Case3-1, 3-2
+        param3 = Parameter("param3")
+        qc.u(param1, param2, param3, 0)  # Case3-1
+        qc.u(param1, param2, param3, 0)
+        qc.data[4] = (RXGate(param1), [qr[0]], [])  # Case3-2
+
+        # Create an expected ParaemterTable for Case3-1, 3-2
+        qc_case3._parameter_table[param1] = [(qc.data[0][0], 0)]
+        qc_case3._parameter_table[param2] = [(qc.data[1][0], 0)]
+        qc_case3._parameter_table[param1].append((qc.data[3][0], 0))
+        qc_case3._parameter_table[param2].append((qc.data[3][0], 1))
+        qc_case3._parameter_table[param3] = [(qc.data[3][0], 2)]
+        qc_case3._parameter_table[param1].append((qc.data[4][0], 0))
+
+        # Assertion for Case3-1, 3-2
+        self.assertEqual(qc._parameter_table, qc_case3._parameter_table)