Add scheduling to ParallelExperiment #1100
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Adds handling for asap and alap scheduling to ParallelExperiment.
chriseclectic
added
the
Changelog: Bugfix
| # Max duration for all components that will be combined into a single circuit | ||
| max_durations = {} | ||
| duration_unit = None | ||
| scheduling_method = getattr(self.transpile_options, "scheduling_method", None) |
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Will it be transpile option? I think we should keep current behavior of delegating this scheduling to sub experiments, and turn this into experiment option of parallel experiment. We should give it another name because the logic you implemented is too much simplified.
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If you set it as a transpile option it will also be set as transpile option for component experiments. In the case where its individual set for component experiments, but not the main parallel one, they could be different values (eg some asap some alap) so there is no way to know how to align the parallel blocks unless there is a method in the main experiment (or you check they are all the same or some other heuristic)
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We can still schedule individual experiment with different policy. Parallel one can prepend or append delay without modulating the individual schedule (the parallel scheduler considers the individual circuit as a block). I think this is another layer of scheduling, and thus we should avoid having the same option. Otherwise user may easily misunderstand the behavior of parallel block scheduling.
| @@ -158,6 +197,18 @@ def _combined_circuits(self, device_layout: bool) -> List[QuantumCircuit]: | |||
| ) from ex | |||
| circuit._append(inst, mapped_qargs, mapped_cargs) | |||
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| # If scheduling method is alap append shorter sub-circuits with delays | |||
| if scheduling_method == "asap" and pad_time: | |||
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I think we can remove this because adding delay after measurement, or adding any instruction to qubit without measurement doesn't make any sense. Then name could be something like delay_sub_circuit_execution: bool, which can avoid confusion with built-in scheduling logic in preset transpiler.
(Edit) We can add some noisy experiment to investigate spectator interaction, but I don't think adding delay impacts the result.
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This was exactly @ajavadia issue though, since backends defaults to alap scheduling if you want to do asap scheduling you need to do this padding or it will change the alignment when it reschedulings things to alap during execution.
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IIRC this is not the case. Backend has meas_map constraints and they align measurements according to the map. I'm not sure if they can trigger measurement at different time.
coruscating
added
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backport stable potential
Summary
Adds handling for asap and alap scheduling to ParallelExperiment.
Details and comments
Fixes
ParallelExperimenthandling ofscheduling_method transpile option for"asap"and"alap"` scheduling to correctly pad the component experiment subcircuits so that the combined circuit has a fixed duration on the experiments physical qubits.