EstimatorV2: from_backend does nothing

[zlatko-minev]

Informations

• Qiskit Aer version: 0.14.1
• Python version: 3.11
• Operating system: Mac

What is the current behavior?

from_backend seems to do nothing.

Steps to reproduce the problem

Take a look at the source code here in EstimatorV2

    def from_backend(self, backend, **options):
        """use external backend"""
        self._backend.from_backend(backend, **options)

The method from_backend is a class method. Not sure why it's called on an instance of the object and it's return is not used to replace self._backend.

What is the expected behavior?

Should update self._backend

Suggested solutions

Maybe the follwiong, not. sure if we need to also update other options, etc. such as in self.options.backend_options

    def from_backend(self, backend, **options):
        """use external backend"""
        self._backend = AerSimulator.from_backend(backend, **options)

[hhorii]

#2120 resolved this issue. Thanks.