Evaporation limited loading of an atom trap

Recently, we have experimentally demonstrated a continuous loading mechanism for an optical dipole trap from a guided atomic beam [1]. The observed evolution of the number of atoms and temperature in the trap are consequences of the unusual trap geometry. In the present paper, we develop a model based on a set of rate equations to describe the loading dynamics of such a mechanism. We consider the collision statistics in the non-uniform trap potential that leads to twodimensional evaporation. The comparison between the resulting computations and experimental data allows to identify the dominant loss process and suggests ways to enhance the achievable steady-state atom number. Concerning subsequent evaporative cooling, we find that the possibility of controlling axial and radial confinement independently allows faster evaporation ramps compared to single beam optical dipole traps.Comment: 10 pages, 7 figure

Contactless nonlinear optics mediated by long-range Rydberg interactions

In conventional nonlinear optics, linear quantum optics1, 2, and cavity quantum electrodynamics3, 4 to create effective photon–photon interactions photons must have, at one time, interacted with matter inside a common medium. In contrast, in Rydberg quantum optics5, 6, 7, 8, 9, 10, optical photons are coherently and reversibly mapped onto collective atomic Rydberg excitations11, giving rise to dipole-mediated effective photon–photon interactions that are long range12, 13. Consequently, a spatial overlap between the light modes is no longer required. We demonstrate such a contactless coupling between photons stored as collective Rydberg excitations in spatially separate optical media. The potential induced by each photon modifies the retrieval mode of its neighbour7, 9, 14, 15, leading to correlations between them. We measure these correlations as a function of interaction strength, distance and storage time, demonstrating an effective interaction between photons separated by 15 times their wavelength. Contactless effective photon–photon interactions16 are relevant for scalable multichannel photonic devices15, 17 and the study of strongly correlated many-body dynamics using light18