qiskit-cold-atom not compatible with qiskit-nature 0.7.1

[fretchen]

Informations

• Qiskit Cold atoms version:

current branch

• Python version:

3.10

• Operating system:

all

What is the current behavior?

Trying to run tests and install qiskit-cold-atom requires to fix qiskit-nature to <= 0.6.2. Otherwise it raises several errors in linting and testing. The main problem seems to be:

No name 'operators' in module 'qiskit_nature'

Steps to reproduce the problem

All problems are produced in this test run.

What is the expected behavior?

We should be able to cleanly work with qiskit-nature in its most current version.

Suggested solutions

[fretchen]

I tried to get started on this one in this branch. However, we have to jump from the syntax of 0.4 to the syntax of 0.7 and this seems to be a fairly major shift. I think that I might have found most of the operators, but some problems and questions remain:

• It would seem that SparseLabelOp is the new name of SecondQuantizedOp ? Not sure what has to be changed to make it work.
• The register_length seems to not exist anymore and had to be updated to num_spin_orbitals or num_spins.
• For the moment the tests still fail with 'Gate rlx has no defined generator'. No idea why.
• I think that we should also enable dependabot updates to avoid another massive version jump like this one in the future.

I was not sure if I should open a PR draft or just get your feedback here. Whatever you guys prefer. Ideas how to solve the issue @eggerdj or @LaurinFischer ?

[eggerdj]

Hi Fred, I think a PR would be good. Like that we can see where the tests fail and comment.

[LaurinFischer]

Hi @fretchen,
I've opened a new branch on my fork where I'm working on this (didn't have permission to push directly onto your PR).
Things are working fine now, but I still have to update the tutorials and some tests.
I'll ping you when everything is working, then I suggest you merge this into your open PR and perhaps ask Daniel to review it.

In the latest qiskit nature, the syntax to initialize SpinOp and FermionicOp changed significantly, which required some refactoring. This means that older versions of qiskit nature will no longer be compatible.