Fix math rendering in some docsstrings of the quantum_info module

[renatomello]

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[MatteoRobbiati]

Thanks, I confirm now it renders properly.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.10%. Comparing base (218f298) to head (5a7fe1e).
Report is 12 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1441   +/-   ##
=======================================
  Coverage   97.10%   97.10%           
=======================================
  Files          81       81           
  Lines       11653    11653           
=======================================
  Hits        11316    11316           
  Misses        337      337           

Flag	Coverage Δ
unittests	97.10% <ø> (ø)

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[MatteoRobbiati]

Thanks! Is the choice of the notation $|v)$ common? Just curiosity :)

[renatomello]

Thanks! Is the choice of the notation | v ) common? Just curiosity :)

yes, either that or double kets like $$|A\rangle\rangle$$

[alecandido]

yes, either that or double kets like | A ⟩⟩

I've also seen the double kets somewhere in the docs. Should we keep just one or the other?

[renatomello]

yes, either that or double kets like | A ⟩⟩

I've also seen the double kets somewhere in the docs. Should we keep just one or the other?

Done

[alecandido]

Done

Thanks @renatomello!