Detection and manipulation of atoms on chips - and elsewhere
Résumé
Cold atoms on chips constitute a fascinating and non-trivial physical system. A gas of atoms can be cooled and trapped in a configuration in which one or more of the dimensions is so tightly confined, that they are "frozen out" leaving a one or two dimensional gas. Such a gas exhibits a rich variety of behavior depending on the interplay between the thermal energy of the atoms and their mutual interactions [1]. At very low temperature, a very dilute gas becomes strongly correlated entering the so-called Tonks-Girardeau regime, while at high density the gas behaves as a quasi-condensate whose density resembles that of a true condensate but whose phase fluctuates. At higher temperatures the gas can behave like an ideal bose gas, or enter a "quantum decoherent" regime in which the gas is strongly degenerate, but in which density fluctuations are large. I will discuss experiments investigating some of these regimes using direct measurements of density fluctuations in a gas on an atom chip. The measurement techniques are closely related to several other correlation techniques introduced recently in the field of cold atoms. These techniques are developing rapidly and I will comment on some of them. [1] K. Kheruntsyan, D. Gangardt, P. Drummond, G. Shlyapnikov, Phys. Rev. A 71, 053615 (2005).