Title: Quantum depletion of a homogeneous Bose-Einstein condensate,
Abstract: We have measured the quantum depletion of an interacting homogeneous
Bose-Einstein condensate, and confirmed the 70-year old theory of N.N.
Bogoliubov. The observed condensate depletion is reversibly tuneable by
changing the strength of the interparticle interactions. Our atomic homogeneous
condensate is produced in an optical-box trap, the interactions are tuned via a
magnetic Feshbach resonance, and the condensed fraction probed by coherent
two-photon Bragg scattering.