Coherent atomic beams from Bose condensates

Kristian Helmerson

Hartmut Wallis, Andreas Röhrl, M. Naraschewski +2 more

We study the coherence of interacting Bose condensates in recent magnetic trap experiments. The coherent evolution manifests itself in the macroscopic interference of two independent Bose condensates. The theoretical predictions from the time-dependent Gross–Pitaevskii equation are in excellent agreement with the measured interference patterns. A coherent coupling of two condensates represents the atomic analogon of a Josephson junction. The dependence of the magnetic confinement on the nuclear spin orientation allows one to build a controllable beam splitter by magnetic resonance. The application of this beam splitter to realize an atom laser is studied theoretically. The coherence of the output beam is limited only by phase diffusion of the condensate.

Thomas P. Altenmüller, Rainer Müller, Axel Schenzle

We investigate the influence of a Bose-Einstein condensate on the coherence properties of a traversing atomic beam. We derive a master equation describing the interaction between beam atoms and the condensate in $s$-wave approximation. Scattering rates are calculated and compared with the case of an ordinary Boltzmann gas. Special attention is paid to the decoherence of the beam, i.e., the decay of spatial coherence in the presence of the condensate. As an application, we explicitly calculate the visibility of the interference pattern in a double-slit experiment and indicate signs for the onset of the condensation.

Michael R. Andrews

Immanuel Bloch, Theodor W. Hänsch, Tilman Esslinger

Using continuous radio-frequency waves a coherent beam of atoms can be extracted from a magnetically trapped gaseous Bose-Einstein condensate. These novel atomic beams have matter-wave properties that are very similar to those of laser light in classical optics and are therefore called atom lasers. Furthermore, coupling out atoms from a Bose gas allows one to probe the dramatic changes in the phase coherence properties of the trapped atomic gas above and below the condensation temperature.

Bongs, Bürger, Sengstock +1 more