[Code together] Add matrix form to Grover Operator

[ingstra]

Issue #1514

Add matrix attribute to Grover template.

[ingstra]

In case you prefer the first one, I'll remove the new private function __getMultiControlledX(self), which I just introduced to not have duplicated code.

[antalszava]

Hi @ingstra, thank you for the submission! 🙂 No clear preference for the approach, other than it producing the correct matrix representation. Overall, the more performant approach would be preferable, though this is not required for us to accept the solution. It could be nice to go with one of them and add further parts of the PR (e.g., testing). Also, don't forget to update the changelog with an entry about the addition and by adding yourself to the list of contributors. 🙂

[codecov]

Codecov Report

Merging #1553 (30bcfe2) into master (c403e27) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1553   +/-   ##
=======================================
  Coverage   99.15%   99.15%           
=======================================
  Files         189      189           
  Lines       13417    13431   +14     
=======================================
+ Hits        13303    13317   +14     
  Misses        114      114           

Impacted Files	Coverage Δ
pennylane/templates/subroutines/grover.py	100.00% <100.00%> (ø)

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[ingstra]

Hi @ingstra, thank you for the submission! slightly_smiling_face No clear preference for the approach, other than it producing the correct matrix representation. Overall, the more performant approach would be preferable, though this is not required for us to accept the solution. It could be nice to go with one of them and add further parts of the PR (e.g., testing). Also, don't forget to update the changelog with an entry about the addition and by adding yourself to the list of contributors. slightly_smiling_face

Ok! Where in the changelog should I write? Top? Bottom?

[ingstra]

Sorry for the billion commits, it's my first time...
Edit: Finally, I think it's good now.

[antalszava]

Hi @ingstra, this is looking nice! 🙂 Overall, it's already in a good shape. Left some suggestions, feel free to address those that were marked as minor last.

Also, there seems to be a conflict in the changelog. This can be resolved by pulling master (git checkout master followed by git pull), switching to the feature branch (git checkout add_reseterror_support) and then merging master (git merge master). The culprit seems to be the changelog file. We'd like to have all the entries kept there, for some reason git could not resolve the addition there well.

[antalszava]

Thank you so much for this contribution @ingstra! 🎉 🙂

[antalszava]

Nice to have this comment!

[antalszava]

Nice!