Experiments in dilute atomic Bose-Einstein condensation

1’1. Why BEC? In the month we began writing this paper, fourteen papers on the explicit topic of Bose-Einstein condensation (BEC) in a dilute gas appeared in the pages of Physical Review. Both theoretical and experimental activity in BEC has expanded dramatically in the three years since the first observation of BEC in a dilute atomic gas. One is tempted t o ask, why? Why is there so much interest in the field? Is this burst of activity something that could have been foreseen, in, say, 1990? We feel the answer to this last question is yes: while “interesting” is a quality which is impossible to define, there was good reason to anticipate, even in 1990, that dilutegas BEC was going to be something worth investigating. To see why, one need only perform the following simple test. Ask any physicist of your acquaintance to compile a list of what he or she considers the six most intriguing physical phenomena that occur at length scales greater than a picorneter and smaller than a kilometer. In our experience. such lists almost always include at least two of the following three effects: superfluidity. lasing. and superconductivity. These three topics all share two common features: counterintuitive behavior and macroscopic occupation of a single quantum state. This then would have been our clue-one might have anticipated that dilute-gas BEC was to be interesting because it shares the same underlying mechanism with the widely appreciated topics of lasing. superfluidity, and superconductivity. and yet is quite different from any