Laser excitation of transverse modes in an atomic waveguide

Cold atoms may travel along narrow waveguides with a strong transverse confinement, perpendicular to the longitudinal propagation axis, in a given transverse oscillation mode and having a well-defined internal state. A laser beam perpendicular to the logitudinal axis may change the internal state and/or the transverse mode. For weak transversal coupling (Lamb-Dicke regime) and the laser on resonance with an internal atomic transition, transverse excitation occurs at "Rabi resonances"-i.e., when the Rabi frequency coincides with the transition frequency between the transverse modes. This provides a route for atomic-state preparation and control in waveguides.