Prof. S Lakshmi Bala from Department of Physics, Madras, India writes a blackboard of equations which show how beamsplitters used alone affect the wavefunctions of input photons. It seems that it depends on the number of photons you use and in which input port to get you a different entangled state. Using 1 in port A and 1 in port B gives a different entangled state than 2 photons on 1 input port and none in the other. The creation and anihillation operators a-dagger, b-dagger are used in association with the beam splitter alone, without use of other elements. Makes me think whether I could discard other elements from my quantum circuit scheme or not.