Fix duration interpolated sweeper for QM

src/qibolab/_core/instruments/qm/controller.py

@@ -348,7 +348,8 @@ def register_duration_sweeper_pulses(
     ):
         """Register pulse with many different durations.
 
-        Needed when sweeping duration.
+        Needed when sweeping duration. When interpolation is used, only
+        a single pulse with the minimum duration is used.
         """
         for pulse in sweeper.pulses:
             if isinstance(pulse, (Align, Delay)):
@@ -359,10 +360,19 @@ def register_duration_sweeper_pulses(
             original_pulse = (
                 pulse if params.amplitude_pulse is None else params.amplitude_pulse
             )
-            for value in sweeper.values.astype(int):
-                sweep_pulse = original_pulse.model_copy(update={"duration": value})
-                sweep_op = self.register_pulse(ids[0], configs[ids[0]], sweep_pulse)
-                params.duration_ops.append((value, sweep_op))
+            values = sweeper.values.astype(int)
+            if sweeper.parameter is Parameter.duration_interpolated:
+                sweep_pulse = original_pulse.model_copy(
+                    update={"duration": min(values)}
+                )
+                params.interpolated_op = self.register_pulse(
+                    ids[0], configs[ids[0]], sweep_pulse
+                )
+            else:
+                for value in values:
+                    sweep_pulse = original_pulse.model_copy(update={"duration": value})
+                    sweep_op = self.register_pulse(ids[0], configs[ids[0]], sweep_pulse)
+                    params.duration_ops.append((value, sweep_op))
 
     def register_amplitude_sweeper_pulses(
         self, args: ExecutionArguments, configs: dict[str, Config], sweeper: Sweeper
@@ -448,6 +458,8 @@ def preprocess_sweeps(
             self.register_amplitude_sweeper_pulses(args, configs, sweeper)
         for sweeper in find_sweepers(sweepers, Parameter.duration):
             self.register_duration_sweeper_pulses(args, configs, sweeper)
+        for sweeper in find_sweepers(sweepers, Parameter.duration_interpolated):
+            self.register_duration_sweeper_pulses(args, configs, sweeper)
 
     def execute_program(self, program):
         """Executes an arbitrary program written in QUA language."""

src/qibolab/_core/instruments/qm/program/arguments.py

@@ -24,6 +24,7 @@ class Parameters:
     duration: Optional[_Variable] = None
     duration_ops: list[tuple[float, str]] = field(default_factory=list)
     interpolated: bool = False
+    interpolated_op: Optional[str] = None
 
     element: Optional[str] = None
     lo_frequency: Optional[int] = None

src/qibolab/_core/instruments/qm/program/instructions.py

@@ -52,7 +52,10 @@ def _play_single_waveform(
     if acquisition is not None:
         acquisition.measure(op)
     else:
-        qua.play(op, element, duration=parameters.duration)
+        if parameters.duration is not None:
+            qua.play(parameters.interpolated_op, element, duration=parameters.duration)
+        else:
+            qua.play(op, element)
 
 
 def _play(