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nulinspiratie / SilQ

Software for quantum control of donor atoms in silicon
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RabiFrequencyFit doesn't always fit well due to bad parametrisation #286

Open maij opened 3 years ago

maij commented 3 years ago

This one is my fault from a while ago.

I added an amplitude and an offset as free fitting parameters for the RabiFrequencyFit, but the amplitude in particular is correlated with the drive strength and detuning which in some extreme conditions can cause large fitting errors to arise.

I think the amplitude should go, and a user can rescale their data if need be. The offset should stay though, as we often have one for ESR Rabi spectra.

nulinspiratie commented 3 years ago

Hmm not sure I agree here. Unless we're performing NMR, the amplitude is a variable not equal to one. So for all ESR fitting, the amplitude should be a free-varying parameter right? Else it's like you have to fit the amplitude by yourself by choosing a few scales and see what "looks" best. Or am I missing something here?

An alternative option could be that we keep the amplitude, but that the default is that it is fixed, i.e. does not vary unless explicitly set. I think this does change the default functionality, meaning that the previous fitting code probably doesn't fit properly anymore.

Can you maybe give some more explanation of what's going wrong here? Does this problem still arise when you explicitly set t? Because usually that's a parameter that's known from experiment.