CosineWindow StatePrep

[KetpuntoG]

Creation of the cosine window, a state whose vector is equivalent to the cosine function:

notes to the reviewer

Instead of the template mentioned in the PRD:

This other one has been used:

This is because in the paper from which it was extracted, it worked with basic states from $-|N/2\rangle$ to $|N/2-1\rangle$ and we work with states from $|0\rangle$ to $|N-1\rangle$. so I have made some adjustments to the rotations to adapt it.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (master@c899d6d). Click here to learn what that means.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #4683   +/-   ##
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  Coverage          ?   99.64%           
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  Files             ?      381           
  Lines             ?    34052           
  Branches          ?        0           
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  Hits              ?    33930           
  Misses            ?      122           
  Partials          ?        0           

Files	Coverage Δ
pennylane/templates/state_preparations/__init__.py	100.00% <100.00%> (ø)
...lane/templates/state_preparations/cosine_window.py	100.00% <100.00%> (ø)

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[KetpuntoG]

[sc-45845]

[soranjh]

Great work @KetpuntoG! left some comments and suggestions.

[soranjh]

Thanks @KetpuntoG, will approve when my minor comments are addressed.

[Jaybsoni]

Looks good 💯! I added a few small comments to improve the look of the docs, but otherwise good work!

[KetpuntoG]

@mudit2812 ready to merge 🚀