Do all observable class operators have associated dynamical variables? Or is there a class of operators that are observable that do not have an associated dynamical variable? It is possible for an operator of quantum mechanics to be unobservable and so it has no associated measurement, like the time evolution operator. But it would appear that the status of observable implies that the operator is that of a dynamical variable or a function of a dynamical variable. What about the case of beamsplitting? In the field theory model we analyse the beamsplitter with creation and annihilation operators that excite or de-excite modes of input and output at the beamsplitter. Does this imply that there is no related dynamical variable to the operators that model the beamsplitting action?
