Introduce requirement setup for integrations

[cosenal]

Description

At the moment, we don't pin the version of integration packages (Braket, Qiskit, etc.) in the Mitiq package that we ship to users. This causes incompatibility issues, e.g, #2208.

This PR introduces integration packages as extra dependencies.

Example: if a user wants to use Mitiq with Qiskit, they can run

pip install mitiq[qiskit]

in their enviroment, and similarly for all other integrations we support. This will guarantee that the version of the integration packages we support are compatible with the ones in the user's environment.

🎪 One important bonus is that now the main Mitiq package only depends on cirq-core as opposed to the full cirq package 🎪

---

This fixes #1201 (see Issue description)

Docs

Readme has been updated.

Note: There will be a lapse of time between merging this PR and the next release, when the README will not be synced with reality of the package. We may consider split the Readme change and ship that along with the release PR. (cc @FarLab as milestone manager.)

Testing

I tested that:

1. for Mitiq developers, everything works just like before with pip install -e .[development]
2. the code snippet from the README works with pip install mitiq (without any extra)
3. the different extra installations for the supported frontend also works (tested started from empty Conda environments)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.22%. Comparing base (44f7c91) to head (d924a34).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2303   +/-   ##
=======================================
  Coverage   98.22%   98.22%           
=======================================
  Files          87       87           
  Lines        4056     4056           
=======================================
  Hits         3984     3984           
  Misses         72       72           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jordandsullivan]

Good idea. I've already hit this issue several times.

[natestemen]

On a high level this looks great. I like this structure a lot! 👍🏻

[cosenal]

@natestemen @jordandsullivan This is now ready to review. Please take a look.

[jordandsullivan]

If we have updated make install to include all these requirements, can we also update this line in the main CONTRIBUTING guide to say make install rather than pip install -e ".[development]"?

[cosenal]

@jordandsullivan Thanks for the thorough review. I addressed / replied to all your comments. PTAL

[jordandsullivan]

Thanks, looks good to me!

[natestemen]

Thanks Alessandro!

Looking forward to this helping users use Mitiq with less dependency issues.

I was brainstorming potential issues that could still arise, and I came up with the following scenario.

1. User gets set up in their desired frontend (not cirq), writing ciruits and running them
2. They learn about Mitiq
3. They run pip install mitiq without looking through the docs too much
4. They hit compatibility issues

If this users then come to us, it should be easy to help solve their problem, as we can ask them to run pip install mitiq[frontend].

This is not a blocker, but I just wanted to write this down both for my understanding¹, and so we all know there are still some potential issues this does not solve. I don't think there's any magic bullet for this problem, however.

Footnotes

1. If I'm misunderstanding something, let me know! ↩

[cosenal]

@natestemen You're right, that's a valid scenario. One way to mitigate it would be to use the tools from pkg_resources to check at runtime (as early as possible) for the dependencies installed in the user environment. Example:

pkg_resources.working_set.require('qiskit~=2.0.0')

VersionConflict: (qiskit 1.0.2 (/opt/miniconda3/envs/mitiqenv/lib/python3.11/site-packages), Requirement.parse('qiskit~=2.0.2')) 

vs.

pkg_resources.working_set.require('qiskit~=1.0.2')

[qiskit 1.0.2 (/opt/miniconda3/envs/mitiqenv/lib/python3.11/site-packages)
...
]

Perhaps something for a follow-up PR, subject to prioritization, in case we get more dependency issues reported.

[natestemen]

Yup agreed, lets only pursue further ideas if we get more complaints. Thanks for jotting down a potential next step :)

[cosenal]

Merged this. After the two reviewers approvals, I have only merged main into the branch and solved the merge conflicts.