Simplify UnitarySynthesis pass test test_qv_natural

[mtreinish]

Summary

The test_qv_natural UnitarySynthesis test is designed to test that when the pulse efficient flag is set on the default unitary synthesis plugin for the UnitarySynthesis pass the output from synthesis is only emitting entangling gates in the natural direction implemented on the target. However, when running on Windows with Python 3.11 and numpy 1.24 we're seeing a non-zero failure rate (in CI it's ~5% across all jobs) of this test likely do to fp precision. When this failure occurs it appears as the failure from detailed in issues #5832, #9177, and others as the test was creating a pass manager that mirrors the optimization loop used in the preset pass managers. The optimization loop is failing to converge on a fixed depth as the unitary synthesis is oscillating between multiple equivalent outputs. However, in this case the test doesn't need the full complexity of the optimization loop as we're just trying to verify the output of unitary synthesis is equivalent with different options and that the output is valid given different options. This can be done with a single iteration of the loop and doesn't require trying to fully optimize the circuit. This commit reduces the complexity of the test to remove the loop from the optimization stage in the custom pass manager so the test is now just running a single iteration of UnitarySynthesis and comparing the output. This will hopefully make the test stable in CI moving forward avoiding this failure mode.

Details and comments

[jakelishman]

I was able to reproduce the failures from this test for various seeds of QuantumVolume on both Windows and macOS with Python 3.10 and 3.11, and Numpy 1.23 and 1.24. The failures we have in CI are just because the particular combination of Windows, Python 3.11 and Numpy 1.24 happen to trigger the bug for seed=15, but the same failure mode is triggered on other combinations with different seeds; the failure is somewhere in the pulse_optimize=True path.

All that said, this test doesn't need a complete loop, and it's blocking CI at the moment, so let's merge.

[jakelishman]

I pushed an empty commit up because the GitHub webhooks had got stuck and failed to trigger the Azure, GHA or CLA runs.

[coveralls]

Pull Request Test Coverage Report for Build 3889078584

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.008%) to 84.632%

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Files with Coverage Reduction	New Missed Lines	%
src/vf2_layout.rs	3	94.74%

Totals
Change from base Build 3885047843:	0.008%
Covered Lines:	64329
Relevant Lines:	76010

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💛 - Coveralls