Fix DynamicCircuitInstructionDurations.from_backend for both Backend versions

[dieris]

Summary

Fixes an issue preventing DynamicInstructionDurations.from_backend(backend) from constructing the corresponding object with a backend whose durations are not in units of dt. Note that prior to Qiskit/qiskit#11501, a InstructionDurations object of the parent class was created instead (with no duration patching).

Details and comments

This is meant to fix the use case for dynamic circuits e.g.

from qiskit.providers.fake_provider import FakeKolkata
from qiskit_ibm_provider.transpiler.passes.scheduling import DynamicCircuitInstructionDurations, ALAPScheduleAnalysis, PadDynamicalDecoupling

durations = DynamicCircuitInstructionDurations.from_backend(FakeKolkata())
pm = PassManager([ALAPScheduleAnalysis(durations),
                  PadDynamicalDecoupling(durations, dd_sequence)])
circ_dd = pm.run(qc)

[dieris]

@mbhealy could you confirm if this fix is still necessary?
@jakelishman this is the issue I was referring to in using DynamicInstructionDurations.from_backend. Is backend.target.durations() the recommended way to load durations for a BackendV2 instead?

[jakelishman]

Diego: Target.durations is most likely correct, and we should probably update the InstructionDurations.from_backend classmethod to call it if it's a BackendV2, I guess. In that case, your subclass of InstructionDurations will still need to override the classmethod in order to lift the return value of Target.duration to your desired form.

[mtreinish]

qiskit.target.durations is the canonical location to get an InstructionDurations object in the BackendV2 model. In general the InstructionDurations class is just a legacy/compatibility view of the information contained in the Target and really is only needed for places that have compatibility with both BackendV1 and BackendV2 and if you're only working in V2 you shouldn't need to use it because the Target class integrates the duration information as part of it's data model.

There is also backend.instruction_durations (https://docs.quantum.ibm.com/api/qiskit/qiskit.providers.BackendV2#instruction_durations) which by default just calls self.target.durations() (https://github.com/Qiskit/qiskit/blob/main/qiskit/providers/backend.py#L411-L414)

[mbhealy]

@mbhealy could you confirm if this fix is still necessary?

Yes, that fix is still important to include.

[dieris]

The new tests and test_transpile_both_paths can only pass with the qiskit fix linked in the description, allowing for the correct creation of a DynamicCircuitInstructionDurations object with patched durations.

[ajavadia]

this looks good. let's merge it soon so this can work with qiskit 1.0

[kt474]

LGTM, @dieris can you make sure these changes are also reflected in qiskit-ibm-runtime?

[coveralls]

Pull Request Test Coverage Report for Build 7809604102

• -6 of 54 (88.89%) changed or added relevant lines in 2 files are covered.
• 9 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 43.323%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_ibm_provider/transpiler/passes/scheduling/utils.py	47	53	88.68%

Files with Coverage Reduction	New Missed Lines	%
qiskit_ibm_provider/transpiler/plugin.py	9	45.16%

Totals
Change from base Build 7805663899:	0.2%
Covered Lines:	2933
Relevant Lines:	6770

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💛 - Coveralls