Fix multiple cycles of staggered DD (#1630)

* Fix staggered DD with insert_multiple_cycles

* release note

---------

Co-authored-by: Kevin Tian <kevin.tian@ibm.com>

qiskit_ibm_runtime/transpiler/passes/scheduling/dynamical_decoupling.py

@@ -448,9 +448,7 @@ def _pad(
             seq_length = np.sum(seq_lengths)
             seq_ratio = self._sequence_min_length_ratios[sequence_idx]
             spacings = self._spacings[sequence_idx]
-            alt_spacings = (
-                np.asarray(self._alt_spacings[sequence_idx]) if self._coupling_map else None
-            )
+            alt_spacings = self._alt_spacings[sequence_idx] if self._coupling_map else None
 
             # Verify the delay duration exceeds the minimum time to insert
             if time_interval / seq_length <= seq_ratio:
@@ -474,8 +472,12 @@ def _pad(
                 seq_lengths = seq_lengths * num_sequences
                 seq_length = np.sum(seq_lengths)
                 spacings = spacings * num_sequences
+                if alt_spacings is not None:
+                    alt_spacings = alt_spacings * num_sequences
 
             spacings = np.asarray(spacings) / num_sequences
+            if alt_spacings is not None:
+                alt_spacings = np.asarray(alt_spacings) / num_sequences
             slack = time_interval - seq_length
             sequence_gphase = self._sequence_phase
 

release-notes/unreleased/1630.bug.rst

@@ -0,0 +1,4 @@
+Fixed the combination of `insert_multiple_cycles` and `coupling_map` options in
+ :class:`.PadDynamicalDecoupling`. This combination allows to select staggered 
+ dynamical decoupling with multiple sequence cycles in each delay that crosses 
+ the threshold set by `sequence_min_length_ratios`. 

test/unit/transpiler/passes/scheduling/test_dynamical_decoupling.py

@@ -989,6 +989,69 @@ def test_staggered_dd(self):
 
         self.assertEqual(qc_dd, expected)
 
+    def test_staggered_dd_multiple_cycles(self):
+        """Test staggered DD with multiple cycles in a single delay"""
+        dd_sequence = [XGate(), XGate()]
+        pm = PassManager(
+            [
+                ASAPScheduleAnalysis(self.durations),
+                PadDynamicalDecoupling(
+                    self.durations,
+                    dd_sequence,
+                    coupling_map=self.coupling_map,
+                    alt_spacings=[0.1, 0.8, 0.1],
+                    sequence_min_length_ratios=[4.0],
+                    insert_multiple_cycles=True,
+                    schedule_idle_qubits=True,
+                ),
+            ]
+        )
+
+        qc_barriers = QuantumCircuit(3, 1)
+        qc_barriers.x(0)
+        qc_barriers.x(1)
+        qc_barriers.x(2)
+        qc_barriers.barrier()
+        qc_barriers.measure(0, 0)
+        qc_barriers.delay(14, 0)
+        qc_barriers.x(1)
+        qc_barriers.x(2)
+        qc_barriers.barrier()
+
+        qc_dd = pm.run(qc_barriers)
+
+        expected = QuantumCircuit(3, 1)
+        expected.x(0)
+        expected.x(1)
+        expected.x(2)
+        expected.barrier()
+        expected.x(1)
+        expected.delay(80, 1)
+        expected.x(1)
+        expected.delay(176, 1)
+        expected.x(1)
+        expected.delay(160, 1)
+        expected.delay(80, 1)
+        expected.x(1)
+        expected.delay(176, 1)
+        expected.x(1)
+        expected.delay(92, 1)
+        expected.x(2)
+        expected.delay(32, 2)
+        expected.x(2)
+        expected.delay(304, 2)
+        expected.x(2)
+        expected.delay(48, 2)
+        expected.delay(32, 2)
+        expected.x(2)
+        expected.delay(304, 2)
+        expected.x(2)
+        expected.delay(44, 2)
+        expected.measure(0, 0)
+        expected.delay(14, 0)
+        expected.barrier()
+        self.assertEqual(qc_dd, expected)
+
     def test_insert_dd_bad_spacings(self):
         """Test DD raises when spacings don't add up to 1."""
         dd_sequence = [XGate(), XGate()]