[QDP] Add NumPy state vector documentation to QDP API

[Rutuja123-dos]

Purpose of PR

This PR adds documentation describing how NumPy arrays are used
to represent quantum state vectors in QDP.

It includes:

• State vector structure and dtype
• A simple NumPy example
• Notes on usage in simulation backends and tests

Fixes #723.

Related Issues or PRs

Closes #723

Changes Made

• Bug fix
• New feature
• Refactoring
• Documentation
• Test
• CI/CD pipeline
• Other

Breaking Changes

• Yes
• No

Checklist

• Added or updated unit tests for all changes
• Added or updated documentation for all changes
• Successfully built and ran all unit tests or manual tests locally
• PR title follows "MAHOUT-XXX: Brief Description" format (if related to an issue)
• Code follows ASF guidelines

[rich7420]

cc @ryankert01

[ryankert01]

@rich7420 I don't think numpy pr is merged or created right now
btw, I think it should merge to dev-qdp instead of main.

[rich7420]

agree. I think we could turn into draft waiting for numpy reader being merged.

[400Ping]

Btw you may need to reopen a pr to target it to dev-qdp

[Rutuja123-dos]

Thank you for the guidance.
I understand that this documentation should target dev-qdp and may depend on the NumPy reader being merged first.
I’ll reopen a new PR against dev-qdp once the relevant changes are ready.
Thanks for your time and review.

[rich7420]

@Rutuja123-dos thanks for the patch!

[400Ping]

And please ask if someone is doing this before pushing a pr, it is not polite to just take over.

[Rutuja123-dos]

Thank you for pointing that out
I’m sorry about that.
I should have checked and coordinated first before pushing the PR.
I’ll make sure to ask on the issue or mailing list before working on similar changes next time.
Thanks for the guidance and review.