Text: Bose condensates make quantum leaps and bounds Feature: August 1999 http://physicsweb.org/article/world/12/8/10 Since the first observation in 1995 of Bose-Einstein condensation in dilute atomic gases, atomic physicists have made extraordinary progress in understanding this unusual quantum state of matter. BOSE-EINSTEIN condensation is a macroscopic quantum phenomenon that was first predicted by Albert Einstein in the 1920s, at a time when quantum theory was still developing and was being applied to microscopic systems, such as individual particles and atoms. Einstein applied the new concept of Bose statistics to an ideal gas of identical atoms that were at thermal equilibrium and trapped in a box. He predicted that at sufficiently low temperatures the particles would accumulate in the lowest quantum state in the box, giving rise to a new state of matter with many unusual properties. The crucial point of Einstein's model is the absence of interactions between the particles in the box. However, this makes his prediction difficult to test in practice. In most real systems the complicating effect of particle interactions causes the gas to solidify well before the temperature for Bose-Einstein condensation is reached. But techniques developed in the past four years have allowed physicists to form Bose-Einstein condensates for a wide range of elements. In the August issue of Physics World magazine, Yvan Castin, Ralph Dum and Alice Sinatra from the Laboratoire Kastler Brossel de l'Ecole Normale Supérieure in Paris, France, describe the latest advances in Bose-Einstein condensation. Further reading M H Anderson et al. 1995 Observations of Bose?Einstein condensation in a dilute atomic vapor Science 269 198 M R Andrews et al. 1997 Observation of interference between two Bose condensates Science 275 637 E A Burt et al. 1997 Coherence, correlations, and collisions: what one learns about Bose?Einstein condensates from their decay Phys. Rev. Lett. 79 337 E A Cornell et al. 1998 Having it both ways: distinguishable yet phase-coherent mixtures of Bose?Einstein condensates Preprint F Dalfovo et al. 1999 Theory of Bose?Einstein condensation in trapped gases Rev. Mod. Phys. 71 463 L V Hau et al. 1997 Light speed reduction to 17 metres per second in an ultracold atomic gas Nature 397 594 S Inouye et al. 1998 Observation of Feshbach resonances in a Bose?Einstein condensate Nature 392 151 D Kleppner et al. 1998 Bose?Einstein condensation of atomic hydrogen Proc. Int. School of Physics "Enrico Fermi" Preprint C Townsend, W Ketterle and S Stringari 1997 Bose?Einstein condensation Physics World March pp29?34 J Walraven 1995 Atomic hydrogen: the quantum gas Physics World July pp37?4

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