Rz has no gradient issue resolved

[PatrickHuembeli]

Hey there, The way RotZ was implemented it didn't have any gradient. I fixed the issue by using the same template as for the RotY and RotX. I think the tl.tensor() in the original version somehow blocked the backprop. The way it is written now the gradient is correct.

[taylorpatti]

Hi Patrick. Thanks for the PR and I agree that you have the right idea to functionalize the rotations of RotZ in as RotX and RotY are in order to fix the gradient problem, but it looks like the nosetests are failing with logical errors in your update.

At a quick glance, looks like a sign/complex number issue, if you'd like to check the functional form I've always really liked this document by Ian Glendinning (e.g., slide 26): https://www.researchgate.net/profile/Ian-Glendinning/publication/268270479_The_Bloch_Sphere/links/54bf7bc30cf2f6bf4e04f133/The-Bloch-Sphere.pdf

More efficient/precise would probably be writing the z-rotation in the second functional form as a single matrix, like it was written before but now functionalized properly as you have pointed out.

[PatrickHuembeli]

Hi Taylor, Sorry for that. I didn't realize that you absorbed the -1j factor into the Paulies. I added this now. So the PauliZ matrix is [[-1j, 0], [0, 1j]]. With the given convention this should return the right unitaries.

[codecov[bot]]

Codecov Report

Merging #4 (0ccc2dd) into main (8b13a64) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main       #4   +/-   ##
=======================================
  Coverage   97.60%   97.60%           
=======================================
  Files          20       20           
  Lines        1545     1548    +3     
=======================================
+ Hits         1508     1511    +3     
  Misses         37       37           

Impacted Files	Coverage Δ
tlquantum/tt_gates.py	99.11% <100.00%> (+0.01%)	:arrow_up:

:mega: Codecov can now indicate which changes are the most critical in Pull Requests. Learn more