I am a beginner in quantum optics and started from reading the Fox's book. I got to Ch.7, where there is a discussion about the amplitude-squeezed states. I am really puzzled by the effect of phase being un-determined in a sense of such phase effects as interference, for instance.
What if I have a beam of number states (I know exactly how many photons are generated per unit time), then my phase information is completely undefined. How can interference be observed in such a system then?
Another question: I know that it is possible to generate quantum structured light such as orbital angular momentum light (OAM). If I have a beam of OAM number states, what does it even mean? How do I know those are OAMs if their phase is undefined (ultimately cannot be quantized)?