Spatial quantum noise interferometry in expanding ultracold atom clouds

The paper reports on measurement on a Mott insulator released from an optical lattice trap. We show that strong periodic quantum correlations exist at the atomic shot noise level between density fluctuations in the expanding atom cloud, reflecting the underlying spatial ordering in the lattice. These spatial correlations find a natural interpretation in terms of a multiple wave HBT interference effect, and provide a unique tool to identify novel quantum phases of ultracold bosonic or fermionic atoms.