Squeezing in Vibronic Spectra example

I have another question to your Vibronic Spectra example.
Especially to strawberryfields.apps.qchem.vibronic and the operations implemented there. In the paper you are referring to (Huh et al.) the squeezing of the state is done by the hermitian conjugate of the squeezing operator. In the code you use the squeezing parameters which are also mentioned in the paper but with the normal squeezing operation. As far as I can see you also use the same conventions on how to define the squeezing operator. Am I missing something or should the squeezing parameters get an additional minus? ( since S\dagger(z)=S(-z) )

Hey @Hendrik,

It seems to me like the paper and what’s in Strawberryfields are using slightly different conventions for how one can write the Doktrov operator. Loosely:

  • Paper (Eq. 19): R S^\dagger R^\dagger D
  • SF (here): DRSR

I assume that the parameters in SF that are used to define each of the four operators above (gbs_params) are calculated in such a way as to reflect the same physics as what’s in Eq 19 of the paper, just a different convention :slight_smile:. For a squeezing operation: S^\dagger(r) = R(pi/2)S(r)R^\dagger(pi/2), so the dagger might have just been absorbed into the rotations on either side.

You can check the decompositions documentation if you want dive deeper!