use diagonal matrix with group commutator

[Edoardo-Pedicillo]

Checklist:

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

[MatteoRobbiati]

Thanks.
The tests errors are due to the dbf_migrate branch, right?

[andrea-pasquale]

Thanks. The tests errors are due to the dbf_migrate branch, right?

Not really, I think that it is better if we fix them in this PR. @Edoardo-Pedicillo feel free to do it whenever you have time otherwise I can do it.

[Sam-XiaoyueLi]

@MatteoRobbiati Hi Matteo, I think this PR broke test_models_dbi.py by removing the line raise_error(ValueError, f"Cannot use group_commutator with matrix {d}"). I'm not sure if we should update the test to reflect the changes or should I try to fix it in my branch (or this?). Please advise. Thanks!

/cc @Edoardo-Pedicillo @andrea-pasquale

[MatteoRobbiati]

@Sam-XiaoyueLi you are right, because now we don't need to raise an error, since we have a default matrix d. I guess the solution is to remove the lines:

    with pytest.raises(ValueError):
        dbf(mode=DoubleBracketGeneratorType.single_commutator, step=0.01)

from the tests.

What do you think @Edoardo-Pedicillo, @andrea-pasquale?

[marekgluza]

@Sam-XiaoyueLi you are right, because now we don't need to raise an error, since we have a default matrix d. I guess the solution is to remove the lines:

    with pytest.raises(ValueError):
        dbf(mode=DoubleBracketGeneratorType.single_commutator, step=0.01)

from the tests.

What do you think @Edoardo-Pedicillo, @andrea-pasquale?

@Sam-XiaoyueLi One comment, maybe others can help to understand the dependancies: I believe d is a numpy array, shouldn't it be Hamiltonian? That way other backends eg hardware won't have an issue?

For now DBI is not deployable because we don't unfold so it's a classical simulator model but I'm preparing to do the transpiler into Hamiltonian simulation and then we will have to switch.

Possible solution: add transpiled_double_bracket.py which inherits and works with appropriate evolution oracles which here would derive from Circuit

[andrea-pasquale]

@Sam-XiaoyueLi you are right, because now we don't need to raise an error, since we have a default matrix d. I guess the solution is to remove the lines:

    with pytest.raises(ValueError):
        dbf(mode=DoubleBracketGeneratorType.single_commutator, step=0.01)

from the tests.

What do you think @Edoardo-Pedicillo, @andrea-pasquale?

Hi all, actually the correct lines to remove should be

    with pytest.raises(ValueError):
        dbf(mode=DoubleBracketGeneratorType.group_commutator, step=0.01)

given that this PR changes only the group_commutator and not the single_commutator.
I've seen that @Sam-XiaoyueLi already performed some fixes in #1143 we can continue the discussion there.