A Mach-Zehnder Interferometer for atomic Bose-Einstein condensates
Prof. Dr. Thorsten Schumm (Atominstitut TU Wien)

We realize the matter-wave equivalent of the optical Mach-Zehnder interferometer on an atom chip. As a first element, we implement a BEC beam splitter based on a tuneable double well potential. A single atom-sensitive imaging system gives access to the conjugate variables number and phase and allows us to characterize the coherent state after the splitting. We find number fluctuations below shot noise (squeezing) due to interactions in the splitting process. We then implement a gravity-dependent phase shifter by spatially tilting the double well. Measuring the phase evolution, we encounter phase diffusion, again due to interactions. We close the interferometer by a novel, non-adiabatic combiner element, mapping relative phase onto site population. Current limitations and further improvements are discussed.