Update SQD guides to mention windows issue?

[javabster]

Currently the SQD guide is not runnable on windows machines because of the pyscf dependency. I think we should add an admonition warning windows users about this, and perhaps include it in all current and future sqd pages?

I'm not sure if there is any specific advice we could give to SQD users with windows machines, maybe @jenglick or @garrison have a suggestion?

[caleb-johnson]

Agree we can beef up support for Windows.

We can:

1. Make pyscf an optional dependency. Users who have the package get access to solve_fermion, users who don't have it will not have access to that function. Installation seamless either way
2. Point users to the pyscf install guide which does a good job of outlining some installation options which could work for Windows users (e.g. Docker, install from source). WIndows users should also be able to use Windows subsystem for Linux to get it running. We could add a Windows section to the install guide and point them there from the Install section of the landing page

[Eric-Arellano]

@caleb-johnson I think both are compelling.

I would definitely encourage the optional dependency because many users are not power-users and may not be comfortable using Docker/install_from_source or WSL, and they may be confused and frustrated that the entire install fails due to one dep they don't even use. For context, this issue was created due to #2595, that we realized Becky couldn't run any of our notebooks anymore locally due to us adding the SQD tutorial.

In case you haven't seen it, Qiskit SDK has really nice support for optional deps, like raising an exception when trying to use an optional dep that has not been installed. https://github.com/Qiskit/qiskit/blob/main/qiskit/utils/optionals.py

[garrison]

Currently the SQD guide is not runnable on windows machines because of the pyscf dependency.

As best I can tell, pyscf should already not be considered a dependency on Windows. I am puzzled as to why it is not working.

[caleb-johnson]

Currently the SQD guide is not runnable on windows machines because of the pyscf dependency.

As best I can tell, pyscf should already not be considered a dependency on Windows. I am puzzled as to why it is not working.

We haven't cut a release since that change. I guess we can just release v0.9 and the installation will work.

@Eric-Arellano , the Fermionic tutorial will still use pyscf directly to build up the molecule, generate the parameters for the ansatz, and run the solver. Also, ffsim has a depdendency on pyscf, which we use in the tutorial to create the ansatz. Windows users will need to get pyscf installed somehow to run the tutorial in its entirety, but the package will be installable and fully available, with the exception of the solver

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