Enhance Sparse Observable Handling and Expand State Initialization

[AmintorDusko]

Enhance Sparse Observable Handling and Expand State Initialization

Summary:

This PR expands the capabilities of our sparse observable handling and add support for state vector initialization with sparse data. Key changes include:

• Sparse Input Support for State Vector Initialization: Enables the initialization of state vectors from sparse input formats, offering improved efficiency for large, sparse systems.
• Extended expval, var, and measures with samples Support: Modified the expval, var, and measures with samples to accept general SparseHermitianObs objects, allowing for extending the calculation of expectation values, variances, and measures with samples to other sparse observables.

Detailed Changes:

• State Vector Initialization:
  • Implemented logic to handle sparse data as input for state vector initialization.
  • Added necessary checks and conversions to ensure compatibility with the internal state representation.
• expval, var, and measures with samples:
  • Modified the functions to accept SparseHermitianObs objects as arguments.
  • Generalized the class handling to make it expandable to other sparse observables.

Related issues

[sc-86157] [sc-85831]

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 98.07692% with 1 line in your changes missing coverage. Please review.

Project coverage is 98.94%. Comparing base (9e26a91) to head (2216056).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
pennylane_lightning/lightning_gpu/_state_vector.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1068      +/-   ##
==========================================
+ Coverage   97.98%   98.94%   +0.95%     
==========================================
  Files         233      266      +33     
  Lines       40090    44752    +4662     
==========================================
+ Hits        39284    44281    +4997     
+ Misses        806      471     -335     

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[JerryChen97]

Thanks a lot! I don't have any blocking suggestions. Just one last question on the scope: from several changes to docstr, it looks like we dropped the wording for batched state. Is it because in the past we didn't actually support the batched states in these interface, or there's plan to move it around somewhere else?

[AmintorDusko]

Thanks a lot! I don't have any blocking suggestions. Just one last question on the scope: from several changes to docstr, it looks like we dropped the wording for batched state. Is it because in the past we didn't actually support the batched states in these interface, or there's plan to move it around somewhere else?

@JerryChen97, I don't have a good answer for you. Perhaps @maliasadi can clarify this subject.

[josephleekl]

Thanks @AmintorDusko! 🎆 Happy to approve, just a non-blocking comment. Also just want to make sure the GPU coverage is OK once all the tests complete

[multiphaseCFD]

Thanks @AmintorDusko . Nice work. Would you mind to trigger the mpi tests as changes are made to the mpi part? Happy to approve once all CIs turn green.

[AmintorDusko]

Thanks @AmintorDusko . Nice work. Would you mind to trigger the mpi tests as changes are made to the mpi part? Happy to approve once all CIs turn green.

Thank you very much!