[Refactor] Better use of projectors

[RolandMacDoland]

Projectors are basic operations in quantum mechanics defined in Qadence by being the outer product between ket and bra bitstrings. It is represented by the ProjectorBlock here.

More complex operations and algorithms can be built on top of projectors. However, there are few places in Qadence where projectors can be used as a replacement for built-in operations. In particular:

• [ ] Measurements protocols:
  • [ ] Shadows (here)
• [ ] Overlap (here and here)

[RolandMacDoland]

@dominikandreasseitz @jpmoutinho Does it sound OK to you guys ?

[jpmoutinho]

Yes 👍

Should it really be changed in the Shadows though? There you use the matrix directly, not the block.

[RolandMacDoland]

Yes 👍

Should it really be changed in the Shadows though? There you use the matrix directly, not the block.

Yes, but you can block_to_tensor it.

[king-p3nguin]

Hi, I would like to work on this issue for unitaryhack.

[RolandMacDoland]

Hi, I would like to work on this issue for unitaryhack.

Hi @king-p3nguin thanks for your interest in working on Qadence ! Feel free to ask questions here if you find anything unclear and raise a PR for your solution.