Fix approximation_degree default in generate_preset_pass_maanger

[jakelishman]

Summary

This brings it inline with transpile, as was done in gh-8595.

Details and comments

I'm proposing this as a candidate for 1.0 despite missing the deadline (needs another maintainer's sign-off) because this is really surprising behaviour, and we decided way back in #8595 that the default of "approximate away literally all of my Trotterisation" was a sufficiently poor default we ought to make the change as a sort-of bugfix. It's even more surprising for generate_preset_pass_manager to do this if transpile isn't.

Fix #11693.

[qiskit-bot]

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[mtreinish]

I'm ok with granting a freeze exception for this PR, it was a good catch by @chriseclectic to find this was mismatched with transpile(). We definitely don't want this as the default and we should definitely get this in before rc1 tomorrow. Just one inline suggestion and then I think we can enqueue this for merging.

[mtreinish]

FWIW, I think was only the case if a backend or target with error properties are set. The default of approximation_degree=None was a short hand of approximate up to the error rate reported in the target. So if there was no error rate it wouldn't approximate the decomposition.

[jakelishman]

tbh I just copied the first sentence of the note from #8595. Happy to change it to whatever you like

[mtreinish]

It's fine this was more just me musing out loud. It's why I didn't leave a concrete suggestion.

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• 57 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 89.507%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	3	93.2%
qiskit/circuit/quantumcircuit.py	54	94.23%

Totals
Change from base Build 7732804564:	0.02%
Covered Lines:	59390
Relevant Lines:	66352

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