Wrong variable names in Fourier analysis in Entanglement Verification

[Chibikuri]

Informations

• Qiskit Ignis version:
  0.4 (I found this bug in the current master branch)
• Python version:
  3.8.1
• Operating system:
  macOS

What is the current behavior?

When I was digging the entanglement verification source, I found one thing probably incorrect.
https://github.com/Qiskit/qiskit-ignis/blob/405efbcf59e2e05306680f9c335040e16cf24e5f/qiskit/ignis/verification/entanglement/analysis.py#L192
In the qiskit/ignis/verification/entanglement/analysis.py line 192, I guess the first term of that line should be
(F, F_m) = (.5*(P0 + P1) + np.sqrt(np.absolute(fft[qn])),
not,
(F, F_m) = (.5*(P0_m + P1_m) + np.sqrt(np.absolute(fft[qn])),
because first term represents the fidelity in the case we don't apply error mitigation.

Steps to reproduce the problem

The result could be different.

What is the expected behavior?

Not error mitigated fidelity should be composed of P0, P1, and C, not P0_m, P1_m, and C.

Suggested solutions

Fixing the variable names

Please let me know if my understanding is incorrect.