Again, as with the preceding section we consider the photon to be partly in each of the component beams, which is a translational state that is a superposition of the translational states of the two component beams. This leads us to a generalization of the term translational state as it is applied to photons.
For a photon to be in a definite translational state it does not require it to be restricted to one beam, but may be associated with two or more beams.
In the mathematics of the theory, each translational state is associated with some wave function of ordinary wave optics, meaning they are superposable.