Berry phase in atom optics
We consider the scattering of an atom by a sequence of two near-resonant standing light waves each formed by two running waves with slightly different wave vectors. Due to opposite detunings of the two standing waves and within the rotating wave approximation, the adiabatic approximation applied to the atomic center-of-mass motion and a smooth turn-on and -off of the interaction, the dynamical phase cancels out and the final state of the atom differs from the initial one only by the sum of the two Berry phases accumulated in the two interaction regions. This phase depends on the position of the atom in a way such that the wave packet emerging from the scattering region will focus, which constitutes a novel method to observe the Berry phase without resorting to interferometric methods.