| We investigate the role of quantum fluctuations in a Bose-Einstein condensate in an optical lattice, where the quantum state of the system deviates strongly from a coherent state description. We demonstrate atom-number squeezed states by using the interference signature from an array of freely expanding condensates as a sensitive probe of their phase variance. We explore applications of these squeezed states and demonstrate the ability to use oscillations in the phase variance of the array as atomic beam splitters. These analogous beam splitters are then used to demonstrate a proof-of-principle interferometer which may offer the possibility of sub shot noise sensitivity. In addition, we induce a dynamical instability and investigate the effect of quantum fluctuations on the behavior of a BEC in this unstable regime. |
