It is possible to get quadrature squeezed light where on one quadrature the uncertainty is less than the of a coherent state while in the other one, orthogonal to it, it is larger. Is it possible, by doing an appropriate angle transformation, to go from a quadrature squeezed state to a photon-number squeezed state (sub-Poissonian distribution)?
Yes it is.
Warning: I’m a theoretician, so everything I say below about something being “easy” is to be taken with a lot of salt
However, I think that in practice, doing a rotation is not a good idea, since the only “easy” rotation is a dephasing, which is a rotation around the origin and does not change the phase/amplitude nature of the squeezing. However, another “not too hard to implement” transformation is a displacement.It is usually closely approximated through interference with a bright coherent state over an almost transparent beamsplitter. Tuning carefully the amplitude of the coherent beam and its relative phase with the squeezed state such that the center of the latter is moved by 90% in phase space, converting the pahse-squeezing into photon number squeezing.
In absolute terms in the phase space, the squeezing direction has not changed, but since the phase of the mean complex amplitude has changed, the direction of what is called photon-number amplitude has changed, which does the trick