qiskit/releasenotes/notes/0.23/upgrade-pulse-builder-and-r...

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---
upgrade:
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The behavior of the pulse builder when a :class:`.Schedule` is called
has been upgraded. Called schedules are internally converted into
:class:`.ScheduleBlock` representation and now reference mechanism is
always applied rather than appending the schedules wrapped by
the :class:`~qiskit.pulse.instructions.Call` instruction.
Note that the converted block doesn't necessary recover the original alignment context.
This is simply an ASAP aligned sequence of pulse instructions with absolute time intervals.
This is an upgrade of internal representation of called pulse programs and thus no API changes.
However the :class:`~qiskit.pulse.instructions.Call` instruction and :class:`.Schedule`
no longer appear in the builder's pulse program.
This change guarantees the generated schedule blocks are always QPY compatible.
If you are filtering the output schedule instructions by :class:`~qiskit.pulse.instructions.Call`,
you can access to the :attr:`.ScheduleBlock.references` instead to retrieve the called program.
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:class:`~qiskit.transpiler.passes.RZXCalibrationBuilder`
and :class:`~qiskit.transpiler.passes.RZXCalibrationBuilderNoEcho` transpiler pass
have been upgraded to generate :class:`.ScheduleBlock`.
This change guarantees the transpiled circuits are always QPY compatible.
If you are directly using :meth:`~qiskit.transpiler.passes.RZXCalibrationBuilder.rescale_cr_inst`,
method from another program or a pass subclass to rescale cross resonance pulse of the device,
now this method is turned into a pulse builder macro, and you need to use this method
within the pulse builder context to adopts to new release.
The method call injects a play instruction to the context pulse program,
instead of returning a :class:`.Play` instruction with the stretched pulse.
fixes:
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The ECR pulse sequence misalignment of :class:`~qiskit.transpiler.passes.RZXCalibrationBuilder`
pass has been fixed. See Qiskit/qiskit-terra/#9013 for details.