Interaction Frame Operator

[MichalKononenko]

I find myself using this snippet of code a bunch in my notebooks

RotatingFrameOperator[BaseHamiltonian_, ReferenceHamiltonian_, ScaledTime_] := 
	MatrixExp[I * ReferenceHamiltonian * ScaledTime] . BaseHamiltonian . 
	MatrixExp[-I * ReferenceHamiltonian * ScaledTime] - ReferenceHamiltonian

However, when I want to move it, I resort to copypasta. Is something like this already in quantum utils? If so, where?

[ihincks]

I don't think this is in there anywhere, and though simple, it seems like a fine thing to have. I'm not sure where it would be put, perhaps somewhere in QuantumSystems. I think the following would be more appropriate in terms of style and nomenclature:

EffectiveHamiltonian[baseHamiltonian_, referenceHamiltonian_, t_] := 
	MatrixExp[I * referenceHamiltonian * t] . baseHamiltonian . 
	MatrixExp[-I * referenceHamiltonian * t] - referenceHamiltonian
RotatingHamiltonian[baseHamiltonian_, referenceHamiltonian_, t_] := 
	MatrixExp[I * referenceHamiltonian * t] . baseHamiltonian . 
	MatrixExp[-I * referenceHamiltonian * t]

It would also make sense to make the output compatible with AverageHamiltonian since that would be a common use case (it might already be, I just always forget if AverageHamiltonian wants a function or a matrix with a time symbol).

[MichalKononenko]

AverageHamiltonian wants a function of time.