Added new Rotosolve optimizer for VQE and matrix decomposition in Pauli operators

[sergiomtzlosa]

New Rotosolve optimizer for the VQE class and a useful function to decompose a matrix into Pauli Operators, this was developed under the umbrella of QuantumSpain project (https://quantumspain-project.es/).

Checklist:

• [ ] Reviewers confirm new code works as expected.
• [ ] Tests are passing.
• [ ] Coverage does not decrease.
• [ ] Documentation is updated.

[MatteoRobbiati]

Is this ready for review @sergiomtzlosa?

[sergiomtzlosa]

Is this ready for review @sergiomtzlosa?

Hi @MatteoRobbiati ,

Yes, absolutely, this is ready to review.

Thanks

[scarrazza]

@sergiomtzlosa could you please send me a (private) message, I have some questions about this contribution.

[sergiomtzlosa]

can I do something to enhance this issue and include it in Qibo?

[scarrazza]

@sergiomtzlosa as discussed a couple of weeks ago this contribution should go to qiboml. cc @MatteoRobbiati @BrunoLiegiBastonLiegi for further instructions.

[BrunoLiegiBastonLiegi]

@sergiomtzlosa could I ask you to open another PR for this in qiboml?

[sergiomtzlosa]

You can open a new PR, but I will study how to add the rotosolve in qiboml, do you have an idea about how we can integrate the code?

[BrunoLiegiBastonLiegi]

Yeah sorry you're right, we are still in an early development stage. Probably for now it is enough to open an issue to remind us about this.

[sergiomtzlosa]

perfect! then please open the issue or pull request in qiboml👍