Fix dd issue in calling PauliString.after. (#6943)

Author: babacry

cirq-core/cirq/transformers/dynamical_decoupling.py

@@ -177,7 +177,13 @@ def _calc_pulled_through(
     clifford_ops_in_moment: list[ops.Operation] = [
         op for op in moment.operations if _is_clifford_op(op)
     ]
-    return input_pauli_ops.after(clifford_ops_in_moment)
+    # TODO(#6946): directly pass clifford_ops_in_moment to input_pauli_ops.after() after #6946 is
+    # fixed.
+    affected_qubits = [q for op in clifford_ops_in_moment for q in op.qubits]
+    all_cliffords_in_gate: ops.CliffordGate = ops.CliffordGate.from_op_list(
+        clifford_ops_in_moment, affected_qubits
+    )
+    return input_pauli_ops.after(all_cliffords_in_gate.on(*affected_qubits))
 
 
 def _get_stop_qubits(moment: circuits.Moment) -> set[ops.Qid]:

cirq-core/cirq/transformers/dynamical_decoupling_test.py

@@ -774,3 +774,61 @@ def test_cross_clifford_pieces_filling_merge():
 6: ───────────────────────────────────────────────────────────PhXZ(a=0.2,x=0.2,z=0.1)───X─────────────────────────@───PhXZ(a=0.8,x=0.8,z=0.5)─────H────────────────────────
 """,
     )
+
+
+def test_pull_through_phxz_gate_case1():
+    """Test case diagrams.
+        Input:
+    a: ───H───────PhXZ(a=0.25,x=-1,z=0)───────@───
+                                              │
+    b: ───H───H───H───────────────────────H───X───
+        Output: expected circuit diagram below.
+    """
+    a = cirq.NamedQubit('a')
+    b = cirq.NamedQubit('b')
+
+    phxz = cirq.PhasedXZGate(axis_phase_exponent=0.25, x_exponent=-1, z_exponent=0)
+    assert_dd(
+        input_circuit=cirq.Circuit(
+            cirq.Moment(cirq.H(a), cirq.H(b)),
+            cirq.Moment(cirq.H(b)),
+            cirq.Moment(phxz(a), cirq.H(b)),
+            cirq.Moment(cirq.H(b)),
+            cirq.Moment(cirq.CNOT(a, b)),
+        ),
+        expected_circuit="""
+a: ───H───X───PhXZ(a=0.25,x=-1,z=0)───X───@───Z───
+                                          │
+b: ───H───H───H───────────────────────H───X───────
+""",
+        schema="XX_PAIR",
+    )
+
+
+def test_pull_through_phxz_gate_case2():
+    """Test case diagrams.
+        Input:
+    a: ───H───────PhXZ(a=0.2,x=-1,z=0)───────@───
+                                              │
+    b: ───H───H───H───────────────────────H───X───
+        Output: expected circuit diagram below.
+    """
+    a = cirq.NamedQubit('a')
+    b = cirq.NamedQubit('b')
+
+    phxz = cirq.PhasedXZGate(axis_phase_exponent=0.2, x_exponent=-1, z_exponent=0)
+    assert_dd(
+        input_circuit=cirq.Circuit(
+            cirq.Moment(cirq.H(a), cirq.H(b)),
+            cirq.Moment(cirq.H(b)),
+            cirq.Moment(phxz(a), cirq.H(b)),
+            cirq.Moment(cirq.H(b)),
+            cirq.Moment(cirq.CNOT(a, b)),
+        ),
+        expected_circuit="""
+a: ───H───X───PhXZ(a=0.1,x=0,z=0.4)───X───@───X───
+                                          │
+b: ───H───H───H───────────────────────H───X───X───
+""",
+        schema="XX_PAIR",
+    )