Manipulation of optical fields by atomic interferometry - Quantum variations on a theme by Young

We analyze the principle of a very general and conceptually simple method for manipulating optical fields by coupling them into a matter waves Young double slit apparatus. The field, nonresonant with the atoms, acts as a 'phase-retarding' medium in one of the arms of the interferometer and shifts the atomic fringe pattern. The method constitutes a simple quantum nondemolition measuring scheme of the photon number. Nonclassical states such as Schroedinger cats and Fock states of the field are generated in the measurement process. This scheme, which would be very difficult to implement in the optical domain, is equivalent to a more feasible and recently proposed Ramsey interference method to measure small microwave fields with beams of Rydberg atoms.