Bragg Scattering as a Probe of Atomic Wavefunctions and Quantum Phase   Transitions in Optical Lattices
  We have observed Bragg scattering of photons from quantum degenerate $^{87}$Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wavefunction whose position and momentum width is Heisenberg-limited. The spatial coherence of the wavefunction leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence. 
Hirokazu Miyake, Georgios A. Siviloglou, Graciana Puentes, David E.   Pritchard, Wolfgang Ketterle, and David M. Weld
cond-mat.quant-gas