Fix InverseCancellation pass to handle gates of different names. (#7383…

…) (#7384)

As reported in GH-7378, the InverseCancellation optimization pass
previously assumed that inverse gate pairs would always share a
common name, but this is not universally true. This commit updates
the pass to search for runs containing any of the gate names in the
gates_to_cancel list, instead of only the first.

Co-authored-by: Bruno Schmitt <bruno.schmitt@epfl.ch>

Co-authored-by: Bruno Schmitt <bruno.schmitt@epfl.ch>
(cherry picked from commit d9ab98f)

Co-authored-by: Kevin Krsulich <kevin.krsulich@ibm.com>

qiskit/transpiler/passes/optimization/inverse_cancellation.py

@@ -124,7 +124,7 @@ def _run_on_inverse_pairs(self, dag: DAGCircuit, inverse_gate_pairs: List[Tuple[
             DAGCircuit: Transformed DAG.
         """
         for pair in inverse_gate_pairs:
-            gate_cancel_runs = dag.collect_runs([pair[0].name])
+            gate_cancel_runs = dag.collect_runs([pair[0].name, pair[1].name])
             for dag_nodes in gate_cancel_runs:
                 for i in range(len(dag_nodes) - 1):
                     if dag_nodes[i].op == pair[0] and dag_nodes[i + 1].op == pair[1]:

test/python/transpiler/test_inverse_cancellation.py

@@ -21,7 +21,7 @@
 from qiskit.transpiler.passes import InverseCancellation
 from qiskit.transpiler import PassManager
 from qiskit.test import QiskitTestCase
-from qiskit.circuit.library import RXGate, HGate, CXGate, PhaseGate, XGate
+from qiskit.circuit.library import RXGate, HGate, CXGate, PhaseGate, XGate, TGate, TdgGate
 
 
 class TestInverseCancellation(QiskitTestCase):
@@ -164,3 +164,15 @@ def test_consecutive_self_inverse_h_x_gate(self):
         gates_after = new_circ.count_ops()
         self.assertNotIn("x", gates_after)
         self.assertEqual(gates_after["h"], 2)
+
+    def test_inverse_with_different_names(self):
+        """Test that inverse gates that have different names."""
+        qc = QuantumCircuit(2, 2)
+        qc.t(0)
+        qc.tdg(0)
+        pass_ = InverseCancellation([(TGate(), TdgGate())])
+        pm = PassManager(pass_)
+        new_circ = pm.run(qc)
+        gates_after = new_circ.count_ops()
+        self.assertNotIn("t", gates_after)
+        self.assertNotIn("tdg", gates_after)