In SQD tutorial, use ffsim for small-scale simulator example

[kevinsung]

URL to the relevant course

https://quantum.cloud.ibm.com/docs/en/tutorials/sample-based-quantum-diagonalization

Select all that apply

• new content request
• typo
• code bug
• out-of-date content
• broken link
• other

Describe the fix or the content request.

Currently it uses N2 sto-6g (16 qubits) but with ffsim we can increase it to N2 6-31g (32 qubits) which is more interesting. The ffsim Sampler also lets you easily add global depolarizing noise.

For new content requests - if the request is accepted, do you want to write the content?

I will write (or already have written) a draft of the proposed content