Displacement operator defined differently from standard literature

[tmancal74]

As pointed out by Ahmed Gharib, the displacement operator returned by the operator_factor class from the package quantarhei.qm.scillators.ho shift by the factor of square root of 2 differently from what is usual in the literature. Full explanation as to why this is so is now part of the documentation, and it can be found here:

https://quantarhei.readthedocs.io/en/latest/classes/qm/ho.html

A simple summary is that the definition of shift operator/displacement operator used in Quantarhei is more convenient in molecular physics. The shift parameter \alpha corresponds to a shift of a coordinate q -> q-\alpha, in a standard definition, one thinks more in a way of "shifting" the creation operator D^{\dagger}{\alpha} a D{\alpha} = a + \alpha.

If no comments appear for 48 hours, I will close this issue.

[tmancal74]

I am closing the issue a consider it solved, as explained above.