Elbow operator

[KetpuntoG]

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---

Context:

[sc-91810]

Description of the Change:

Adding the elbows operators described in: https://arxiv.org/abs/1805.03662

Benefits:

More efficient decomposition in templates

Possible Drawbacks:

Right now we can't apply MCMs, we will have to update the operator in the future for the Adjoint(elbow)
Related GitHub Issues:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.68%. Comparing base (362d9e3) to head (5ec2b92).
⚠️ Report is 407 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7472   +/-   ##
=======================================
  Coverage   99.68%   99.68%           
=======================================
  Files         530      531    +1     
  Lines       52148    52224   +76     
=======================================
+ Hits        51985    52061   +76     
  Misses        163      163           

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[dwierichs]

Nice and clear addition! 💯
I left a series of initial comments, nothing fundamental or major :)

[dwierichs]

Everything looks good to go from my side.
I'll approve once the name is finalized! :)

[soranjh]

Thanks @KetpuntoG, left some comments on the docs.

[dwierichs]

I just had some final non-blocking comments, except for the request to add a comment in the example about the output state having to be |0>, and to test the alias to actually be an alias, not just some functional op.

[dwierichs]

Nice, thanks for the quick amendments 💯 🙏
Great job @KetpuntoG

[AntonNI8]

Thanks again!