Continuous detection of an atom laser beam

We have demonstrated a detection scheme for atom laser beams that allows for a continuous measurement of the atom density and readout of the data in real-time. The atoms in the atom laser beam are transferred locally from the lower to the upper hyperfine ground state of ${}^{87}$Rb by coherent coupling and are subsequently detected by an absorption measurement. The detection is non-destructive to the Bose-Einstein condensate in the magnetic trap and the atom laser beam remains unaffected outside the detection region.