Provide options in the cut-finder API to turn LO gate and wire cut finding off or on, expose min-reached flag.

[ibrahim-shehzad]

Add fields gate_lo and wire_lo to OptimizationParameters in cutting.automated_cut_finding.py to allow the user to turn LO gate and wire cutting off or on. The default is to have them both on.

To do:

• Enabling only wire cutting causes multiple tests to fail. The same thing will likely happen if only gate cutting is enabled. Test both of these out and fix these tests.
• Add tests for the CutBothWires action. While running the cut-finder on some circuits with gate_lo set to False (so only wire cut finding enabled), this action was implemented and we realized that there were some new bugs that were not covered by the existing tests.
• Decide if pieces of the code that track the cost of LOCC wire cuts should be removed completely (cf LO circuit cuts optimizer #471 (comment)).
• Remove any pieces of the code that were excluded from coverage because they were tied to the rarely invoked CutBothWires instances.
• Expose metadata field to check if minimum was reached, update tutorial, update tests, and clarify in release note that if the search is terminated early, this flag can give a false negative.

[garrison]

One might want to investigate what happens when one sets both gate_lo and gate_lo to False. Ideally this will result in an informative error message (right?).

[ibrahim-shehzad]

Yes, for sure.

[garrison]

Also, I want to acknowledge somewhere (i.e., in this comment) that we'll probably change the name of gate_lo eventually. since I doubt it makes any sense to implement LOCC gate cutting now that https://arxiv.org/abs/2312.11638 is out. I cannot think of a better name right this moment. The proper names will depend how far we get implementing parallel and black box cutting from that paper.

[ibrahim-shehzad]

I have gone ahead and added some of the updates that we discussed (7fcfcb1).

[garrison]

ibrahim-shehzad added this to the 0.7.2 milestone

This adds a feature, so it (as a whole) will have to wait for 0.8.0. It might be that some of the fixes are worth backporting, though.

[coveralls]

Pull Request Test Coverage Report for Build 9295628099

Details

• 30 of 30 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 9290071298:	0.0%
Covered Lines:	2401
Relevant Lines:	2401

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💛 - Coveralls

[ibrahim-shehzad]

Instances of the greedy search (warm start) algorithm still had access to the LOCC wire-cut cost function and did, in certain instances (when only wire cutting was enabled and the greedy search algorithm was being tested out), output costs that were inconsistent with the LO-only scenario that we currently support. This has now been changed to make things consistent and cost functions that track LOCC wire cuts are no longer exposed anywhere.

[caleb-johnson]

This looks good. Only a couple of very minor nitpicks.

I wonder if this could've been two PRs but looks good to me as-is

[garrison]

Thank you -- I am happy with this. 🚀