Ultracold quantum matter

Abstract:

We combine an RF-dressed magnetic trap with an optical potential to produce a toroidal trapping potential for ultracold 87Rb atoms. We load atoms into this ring trap from a conventional magnetic trap and compare the measured oscillation frequencies with theoretical predictions. This method of making a toroidal trap gives a high degree of flexibility such as a tuneable radius and variable transverse oscillation frequency. The ring trap is ideal for the creation of a multiply connected Bose-Einstein condensate (BEC) and the study of persistent flow and we propose a scheme for introducing a flow of the atoms around the ring. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Abstract:

We present a method of transferring a cold atom between spatially separated microtraps by means of a Raman transition between the ground motional states of the two traps. The intermediate states for the Raman transition are the vibrational levels of a third microtrap, and we determine the experimental conditions for which the overlap of the wavefunctions leads to an efficient transfer. There is a close analogy with the Franck-Condon principle in the spectroscopy of molecules. The spin-dependent manipulation of neutral atoms in microtraps has important applications in quantum information processing. We also show that, starting with several atoms, precisely one atom can be transferred to the final potential well hence giving deterministic preparation of single atoms. © 2007 IOP Publishing Ltd.

Abstract:

We predict the resonance-enhanced magnetic field dependence of atom-dimer relaxation and three-body recombination rates in a Rb87 Bose-Einstein condensate close to 1007 G. Our exact treatments of three-particle scattering explicitly include the dependence of the interactions on the atomic Zeeman levels. The Feshbach resonance distorts the entire diatomic energy spectrum, causing interferences in both loss phenomena. Our two independent experiments confirm the predicted recombination loss over a range of rate constants that spans four orders of magnitude. © 2007 The American Physical Society.

Abstract:

We manipulate a Bose-Einstein condensate using the optical trap created by the diffraction of a laser beam on a fast ferroelectric liquid crystal spatial light modulator. The modulator acts as a phase grating which can generate arbitrary diffraction patterns and be rapidly reconfigured at rates up to 1 kHz to create smooth, time-varying optical potentials. The flexibility of the device is demonstrated with our experimental results for splitting a Bose-Einstein condensate and independently transporting the separate parts of the atomic cloud. © 2006 The American Physical Society.