Matthew

Hi @BrunoLiegiBastonLiegi , so sorry for the delay as I had some deadlines in the past 2 weeks. The code should be ready to go now!

Sorry @BrunoLiegiBastonLiegi , quick question. With reference to this [helper function](https://github.com/qiboteam/qibo/pull/1587#discussion_r2160938361), we should accept numpy arrays, torch tensors, or cupy arrays. While waiting for advice for cupy, I allow for...

Replying to this comment: > that way you don't build the gates for nothing true, you only build them if they are valid, but this is a very inexpensive operation...

Sorry @BrunoLiegiBastonLiegi , how do we get the tests to run with the `@cache`? Running into an error now: `src/qibo/tomography/gate_set_tomography.py:25:1: E0602: Undefined variable 'cache' (undefined-variable)`

Sorry for the very long delay. I have made some suggested changes!