Clarify docstring: Pauli-types conjugate() is complex conjugate, not Hermitian conjugate

[aeddins-ibm]

Environment

• Qiskit version: 1.2
• Python version: 3.11
• Operating system: macOS

What is happening?

Not strictly a bug, just a doc clarification.

The docstring for the conjugate method of Pauli is:

Return the conjugate of each Pauli in the list.

and for SparsePauliOp is

Return the conjugate of the SparsePauliOp.

Personally, when I hear "conjugate of an operator" I think Hermitian conjugate. To avoid confusion with Hermitian conjugate, can we change the docstring of conjugate for Pauli, SparsePauliOp, etc to specify explicitly:

Return the complex conjugate of each Pauli in the list.

and

Return the complex conjugate of the SparsePauliOp.

(It's also weird there's a reference to a "list" in the docstring for a single Pauli, but I'm not concerned about that here).

How can we reproduce the issue?

n/a

What should happen?

n/a

Any suggestions?

No response

[Cryoris]

I would agree, that can be confusing. Would you like to open an issue to fix this? 🙂

[boonware]

@Cryoris Can you assign this to me, please? A fix is in this PR: #13312

[aeddins-ibm]

Thanks all -- would it be worth doing this for SparsePauliOp as well?

It would be updating the description of conjugate that shows up here in the docs: https://docs.quantum.ibm.com/api/qiskit/qiskit.quantum_info.SparsePauliOp#conjugate

However I do not see where this string is defined in qiskit's code.

[boonware]

@aeddins-ibm Indeed, it looks like there are more references that could do with updating. I have created an issue and will tackle this soon: #13322