Fix error in schedule -> signal conversion for schedules with barrier instructions (#203)

Author: DanPuzzuoli

qiskit_dynamics/pulse/pulse_to_signals.py

@@ -163,9 +163,9 @@ def get_signals(self, schedule: Schedule) -> List[DiscreteSignal]:
             )
 
         for start_sample, inst in schedule.instructions:
-            chan = inst.channel.name
-            phi = phases[chan]
-            freq = frequency_shifts[chan]
+            # get channel name if instruction has it
+            chan = inst.channel.name if hasattr(inst, "channel") else None
+
             if isinstance(inst, Play):
                 # get the instruction samples
                 inst_samples = None
@@ -178,8 +178,8 @@ def get_signals(self, schedule: Schedule) -> List[DiscreteSignal]:
                 times = self._dt * (start_sample + np.arange(len(inst_samples)))
                 samples = inst_samples * np.exp(
                     Array(
-                        2.0j * np.pi * freq * times
-                        + 1.0j * phi
+                        2.0j * np.pi * frequency_shifts[chan] * times
+                        + 1.0j * phases[chan]
                         + 2.0j * np.pi * phase_accumulations[chan]
                     )
                 )

releasenotes/notes/0.4/0.4-summary-3de98711c3b7aa09.yaml

@@ -83,6 +83,9 @@ fixes:
     :class:`~qiskit.pulse.instructions.SetFrequency` and
     :class:`~qiskit.pulse.instructions.ShiftFrequency` instructions has also been fixed. (`#140
     <https://github.com/Qiskit/qiskit-dynamics/issues/140>`__)
+  - |
+    :class:`.InstructionToSignals` has been updated to fix an error when parsing schedules that
+    include barrier instructions. `#202 <https://github.com/Qiskit/qiskit-dynamics/issues/202>`__)
   - |
     Fixes a bug in the automatic jit-compilation of :meth:`Solver.solve` when using the ``t_eval``
     kwarg with a JAX method and ``Array.default_backend() == 'jax'``. The bug is fixed by updating

test/dynamics/pulse/test_pulse_to_signals.py

@@ -20,6 +20,7 @@
 from qiskit import pulse
 from qiskit.pulse import Schedule
 from qiskit.pulse.transforms.canonicalization import block_to_schedule
+from qiskit.providers.fake_provider import FakeQuito
 from qiskit import QiskitError
 
 from qiskit_dynamics.pulse import InstructionToSignals
@@ -320,6 +321,27 @@ def test_InstructionToSignals(self):
         signals = converter.get_signals(block_to_schedule(schedule))
         self.assertAllClose(signals[0].samples, gauss_get_waveform_samples, atol=1e-7, rtol=1e-7)
 
+    def test_barrier_instructions(self):
+        """Test correct parsing of schedule with barrier instructions."""
+
+        # this example needs any backend with at least 2 qubits
+        backend = FakeQuito()
+
+        with pulse.build(backend) as sched_block:
+            pulse.play(pulse.Constant(duration=3, amp=0.5), pulse.DriveChannel(0))
+            pulse.barrier(0, 1)
+            pulse.play(pulse.Constant(duration=3, amp=-0.5), pulse.DriveChannel(1))
+
+        converter = InstructionToSignals(
+            dt=1.0, carriers={"d0": 1.0, "d1": 1.0}, channels=["d0", "d1"]
+        )
+        sched = block_to_schedule(sched_block)
+
+        sigs = converter.get_signals(sched)
+
+        self.assertAllClose(sigs[0].samples, np.array([0.5, 0.5, 0.5, 0.0, 0.0, 0.0]))
+        self.assertAllClose(sigs[1].samples, np.array([0.0, 0.0, 0.0, -0.5, -0.5, -0.5]))
+
 
 class TestPulseToSignalsJAXTransformations(QiskitDynamicsTestCase, TestJaxBase):
     """Tests InstructionToSignals class by using Jax."""