Fix Rabi length signal fit

[rodolfocarobene]

Closes #879.

I guess that the "problem" arises from the fact that in rabi length we expect to see oscillations given by detuning (potential at least) spanning along a large duration. While for rabi amplitude the length is usually kept small -> we do not fit oscillation and we don't have the same problem.

I'm not sure that I like the asymmetry, but it doesn't probably matter

Checklist:

• [ ] Reviewers confirm new code works as expected.
• [ ] Tests are passing.
• [ ] Coverage does not decrease.
• [ ] Documentation is updated.
• [ ] Compatibility with Qibo modules (Please edit this section if the current pull request is not compatible with the following branches).
  • [ ] Qibo: master
  • [ ] Qibolab: main
  • [ ] Qibolab_platforms_qrc: main

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.34%. Comparing base (e66294c) to head (9afd229).

Additional details and impacted files

[](https://app.codecov.io/gh/qiboteam/qibocal/pull/884?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) ```diff @@ Coverage Diff @@ ## main #884 +/- ## ========================================== - Coverage 97.37% 97.34% -0.03% ========================================== Files 115 115 Lines 8678 8679 +1 ========================================== - Hits 8450 8449 -1 - Misses 228 230 +2 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibocal/pull/884/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibocal/pull/884/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `97.34% <100.00%> (-0.03%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/qiboteam/qibocal/pull/884?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [src/qibocal/protocols/rabi/utils.py](https://app.codecov.io/gh/qiboteam/qibocal/pull/884?src=pr&el=tree&filepath=src%2Fqibocal%2Fprotocols%2Frabi%2Futils.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#diff-c3JjL3FpYm9jYWwvcHJvdG9jb2xzL3JhYmkvdXRpbHMucHk=) | `100.00% <100.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/qiboteam/qibocal/pull/884/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam)