  The spatial coherence of an atomic wavepacket can be detected in the
scattered photons, even when the center-of-mass motion is in the quantum
coherent superposition of two distant, non-overlapping wave packets. Spatial
coherence manifests itself in the power spectrum of the emitted photons, whose
spectral components can exhibit interference fringes as a function of the
emission angle. The contrast and the phase of this interference pattern provide
information about the quantum state of the center of mass of the scattering
atom.

Quantum Physics;Other Condensed Matter