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 ${}^{87}\mathrm{Rb}$ by coherent coupling and are subsequently detected by an absorption measurement. The detection does not affect the Bose-Einstein condensate in the magnetic trap or the atom laser beam outside the detection region.