J. Arlt

Dynamics of F = 2 Spinor Bose-Einstein Condensates

We experimentally investigate and analyze the rich dynamics in F=2 spinor Bose-Einstein condensates of 87Rb. An interplay between mean-field driven spin dynamics and hyperfine-changing losses in addition to interactions with the thermal component is observed. In particular, we measure conversion rates in the range of 10(-12) cm(3) s(-1) for spin-changing collisions within the F=2 manifold and spin-dependent loss rates in the range of 10(-13) cm(3) s(-1) for hyperfine-changing collisions. We observe polar behavior in the F=2 ground state of 87Rb, while we find the F=1 ground state to be ferromagnetic. We further see a magnetization for condensates prepared with nonzero total spin.

Observation of Phase Fluctuations in Elongated Bose-Einstein Condensates

The occurrence of phase fluctuations due to thermal excitations in Bose-Einstein condensates (BECs) is studied for a variety of temperatures and trap geometries. We observe the statistical nature of the appearance of phase fluctuations and characterize the dependence of their average value on temperature, number of particles, and the trapping potential. We find pronounced phase fluctuations for condensates in very elongated traps in a broad temperature range. The results are of great importance for the realization of BEC in quasi-1D geometries, for matter wave interferometry with BECs, as well as for coherence properties of guided atom laser beams.

Twin Matter Waves for Interferometry Beyond the Classical Limit

An entangled state of up to 10,000 atoms is used to enhance the resolution of an atomic interferometer. Interferometers with atomic ensembles are an integral part of modern precision metrology. However, these interferometers are fundamentally restricted by the shot noise limit, which can only be overcome by creating quantum entanglement among the atoms. We used spin dynamics in Bose-Einstein condensates to create large ensembles of up to 104 pair-correlated atoms with an interferometric sensitivity −1.61−1.1+0.98decibels beyond the shot noise limit. Our proof-of-principle results point the way toward a new generation of atom interferometers.

Observation of the scissors mode and evidence for superfluidity of a trapped bose-einstein condensed Gas

We report the observation of the scissors mode of a Bose-Einstein condensed gas of 87Rb atoms in a magnetic trap, which gives direct evidence of superfluidity in this system. The scissors mode of oscillation is excited by a sudden rotation of the anisotropic trapping potential. For a gas above T(c) (normal fluid) we detect the occurrence of oscillations at two frequencies, with the lower frequency corresponding to the rigid body value of the moment of inertia. Well below T(c) the condensate oscillates at a single frequency, without damping, as expected for a superfluid.

Routes Towards Anderson-Like Localization of Bose-Einstein Condensates in Disordered Optical Lattices

We investigate, both experimentally and theoretically, possible routes towards Anderson-like localization of Bose-Einstein condensates in disordered potentials. The dependence of this quantum interference effect on the nonlinear interactions and the shape of the disorder potential is investigated. Experiments with an optical lattice and a superimposed disordered potential reveal the lack of Anderson localization. A theoretical analysis shows that this absence is due to the large length scale of the disorder potential as well as its screening by the nonlinear interactions. Further analysis shows that incommensurable superlattices should allow for the observation of the crossover from the nonlinear screening regime to the Anderson localized case within realistic experimental parameters.

Detecting Multiparticle Entanglement of Dicke States

Recent experiments demonstrate the production of many thousands of neutral atoms entangled in their spin degrees of freedom. We present a criterion for estimating the amount of entanglement based on a measurement of the global spin. It outperforms previous criteria and applies to a wider class of entangled states, including Dicke states. Experimentally, we produce a Dicke-like state using spin dynamics in a Bose-Einstein condensate. Our criterion proves that it contains at least genuine 28-particle entanglement. We infer a generalized squeezing parameter of -11.4(5)  dB.

Waveguide for Bose-Einstein condensates

We report on the creation of Bose-Einstein condensates of

Ultraviolet light-induced atom desorption for large rubidium and potassium magneto-optical traps

{}^{87}\mathrm{Rb}

Measurement of the spatial correlation function of phase fluctuating Bose-Einstein condensates.

in a specially designed hybrid, optical dipole and magnetic trap. This trap naturally allows the coherent transfer of matter waves into a pure optical dipole potential waveguide based on a doughnut beam. Specifically, we present studies of the coherence of the ensemble in the hybrid trap and during the evolution in the waveguide by means of an autocorrelation interferometer scheme. We observe a mean-field dominated acceleration in the waveguide on a much longer time scale than in the free three-dimensional expansion.

Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate.

We show that light-induced atom desorption (LIAD) can be used as a flexible atomic source for large