An Interferometer for Atoms with Standing Light Waves
All experimentally realized atom interferometers may be divided into two classes. In atomic state interferometers,1,2 the beam splitter produces a superposition of internal states. The process of producing the superposition of internal states is the mechanism for coherently splitting the beams. In the other class of interferometers the beam splitter does not change the internal state of the atom. Rather, diffraction produces a superposition of external states and thus directly creates distinctly different paths in real space. In these de Broglie wave interferometers the beam splitting process — up till now only realized by diffraction at material double slits or material gratings — is directly linked to the wave nature of the external motion.