Exploring strongly correlated quantum matter with ultracold atoms in optical lattices
Prof. I. Bloch, University Mainz
At the heart of a Bose-Einstein condensate lies its description as a single giant matter wave. Such a Bose-Einstein condensate represents the most "classical" form of a matter wave, just as an optical laser emits the most classical form of an electromagnetic wave. Beneath this giant matter wave, however, the discrete atoms represent a crucial granularity, i.e. a quantization of this matter wave field, which has been inaccessible to experiments with Bose-Einstein condensates up to now. I will report on several of our most recent experiments carried out with Bose-Einstein condensates in three-dimensional optical lattices, where this matter wave quantization leads to dramatic effects in the behaviour of the many-body system. For example by controlling the potential depth of the optical lattice we are able to induce a quantum phase transition from a superfluid to a Mott insulating state, which is dominated by strong correlations between the atoms and which constitutes a natural large quantum register for quantum information. In a latest series of new experiments we have been able to show that by observing spatial quantum noise correlations of expanding atom clouds, Hanbury-Brown Twiss bunching of atoms can be observed, which yields novel information about the many body quantum states in the lattice.