[Capture] Capture the single_qubit_fusion transform

[PietropaoloFrisoni]

Context: single_qubit_fusion can now be captured. That is, it can be applied when qml.capture.enabled is True.

Description of the Change: As above.

Benefits: One more transform can be applied with the new capture feature.

Possible Drawbacks: The order of operations might change compared to the non-captured version of this function, but this does not affect the correctness of the result.

Related GitHub Issues: None.

[sc-83906]

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.60%. Comparing base (64e226f) to head (3acbdaf).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #6945    +/-   ##
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  Coverage   99.60%   99.60%            
========================================
  Files         484      484            
  Lines       46141    46243   +102     
========================================
+ Hits        45957    46059   +102     
  Misses        184      184            

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[dwierichs]

Nice work @PietropaoloFrisoni, very thorough testing 💪 💯

I had a number of minor technical suggestions and questions.
I think the occasional reordering through the transform is not problematic, but I would like to make sure that I understand where exactly it comes in :) Do we have other plxpr transforms that do such shenanigans? 😁

[andrijapau]

First pass through, everything looks great to me so far! I think I might have some ways to clean-up my merge rotations PR now ... 😆

[andrijapau]

Another pass through! 😎

[dwierichs]

Thanks for addressing all my comments so thoroughly, @PietropaoloFrisoni 💯
Nice job! 🎉

[andrijapau]

This looks really nice to me! Great job 🚀