Inverse state mapper

[kwkbtr]

No description provided.

[github-actions]

🚀 Deployed on https://deploy-preview-154--quri-parts.netlify.app

[kwkbtr]

Moving post-selection filter functions from quri_parts.chem to quri_parts.openfermion is a breaking change, so let's note it explicitly in pull request description.

[kwkbtr]

This docstring needs to be updated.

[dchung0741]

I haven't read the post selection functions yet, but I have one question about the updated interface for incorporating the inverse mappers.
It looks like the inverse mapper could take in the n_up_spins argument.
For the SCBK Hamiltonian mapping, it also needs to take in n_up_spins in order to compute the correct parity factor for the Hamiltonians.
So my question is: Should we add the n_up_spins argument to the get_state_mapper, get_of_operator_mapper methods as well?

[kwkbtr]

Should we add the n_up_spins argument to the get_state_mapper, get_of_operator_mapper methods as well?

I guess

• For get_of_operator_mapper: Yes
• For get_state_mapper: I think the number of up spins can be determined from the input (occupation numbers). But it is also the case for n_fermions, so I think it's good to add it for consistency.

[dchung0741]

The code looks good to me overall. Just one slight concern.
Also, about the n_up_spins should I add it in my PR later?

[dchung0741]

I'm wondering if this method should be public?
My concern is that for SCBK inverse mapping, we do not rearrange the dropped qubit back to the M/2-th and M-th qubit with this method (M is the number of spin orbitals.) Would this cause user's confusions if they decide to use it as a public method?

[kwkbtr]

Yeah, maybe we can make it private (or you can call it "protected", a term used in other programming languages like C++ or Java).

[toru4838]

I will make it protected in this PR

[toru4838]

Thank you for your feedback!

Also, about the n_up_spins should I add it in my PR later?

This PR only considers restricted (OF's) transformations, so we don't need n_up_spins for get_operator_mapper() and get_state_mapper() here. Let's add it in your PR later.