Fix a transpile issue of BackendSampler

[t-imamichi]

Summary

BackendSampler raises an error if two runs are called sequentially as follows. This PR fixes the issue.
This PR is straightforward. So, it might be better to skip circuits that are already transpiled.

from qiskit import Aer, QuantumCircuit
from qiskit.primitives import BackendSampler

sampler = BackendSampler(Aer.get_backend('aer_simulator'))

qc1 = QuantumCircuit(1,1)
qc1.h(0)
qc1.measure(0, 0)
qc2 = QuantumCircuit(1,1)
qc2.x(0)
qc2.measure(0, 0)

print(sampler.run([qc1]).result())  # OK
print(sampler.run([qc2]).result())  # NG

output

SamplerResult(quasi_dists=[{1: 0.5078125, 0: 0.4921875}], metadata=[{'shots': 1024}])
Traceback (most recent call last):
  File "/home/ima/github/qiskit/terra/tmp/backendsampler.py", line 14, in <module>
    print(sampler.run([qc2]).result())
  File "/home/ima/github/qiskit/terra/qiskit/primitives/primitive_job.py", line 50, in result
    return self._future.result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 451, in result
    return self.__get_result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
    raise self._exception
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/ima/github/qiskit/terra/qiskit/primitives/backend_sampler.py", line 149, in _call
    bound_circuits = [
  File "/home/ima/github/qiskit/terra/qiskit/primitives/backend_sampler.py", line 150, in <listcomp>
    transpiled_circuits[i]
IndexError: list index out of range

Details and comments

[qiskit-bot]

Thank you for opening a new pull request.

Before your PR can be merged it will first need to pass continuous integration tests and be reviewed. Sometimes the review process can be slow, so please be patient.

While you're waiting, please feel free to review other open PRs. While only a subset of people are authorized to approve pull requests for merging, everyone is encouraged to review open pull requests. Doing reviews helps reduce the burden on the core team and helps make the project's code better for everyone.

One or more of the the following people are requested to review this:

• @Qiskit/terra-core
• @ajavadia
• @ikkoham
• @levbishop
• @t-imamichi

[coveralls]

Pull Request Test Coverage Report for Build 3628568741

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.002%) to 84.588%

---

Files with Coverage Reduction	New Missed Lines	%
src/sabre_swap/layer.rs	1	98.43%
qiskit/pulse/library/waveform.py	3	91.49%

Totals
Change from base Build 3619413698:	-0.002%
Covered Lines:	63093
Relevant Lines:	74589

---

💛 - Coveralls

[ikkoham]

Thank you. Good catch! LGTM

[ikkoham]

@t-imamichi Could you write the release note, please?

[t-imamichi]

This PR is straightforward and it transpiles all circuits even if some of them are already transpiled in the past. Do you think we need to optimize the transpilation?

[t-imamichi]

I made an optimized version t-imamichi/qiskit-terra@fix-backend-sampler...t-imamichi:qiskit-terra:fix-bs2
Which do you prefer, @ikkoham?

[ikkoham]

I'm fine with both. I optimized the transpiration in Aer.
https://github.com/Qiskit/qiskit-aer/blob/main/qiskit_aer/primitives/sampler.py#L194-L196

But, skip_transpilation may be exposed to public in the future.
#9074
If we introduce this, we need to fix the transpilation code. (Whether to expose or not should be discussed in the refactor PR.)

[t-imamichi]

If AerSampler does the optimization, it seems good to do it for BackendEstimator too. I will merge it #9236 (comment).

[ikkoham]

LGTM!