Bose-Einstein condensation of an atomic gas

It is now possible to produce in the laboratory ultra-cold gases whose prop erties are very far from intuition. A large fraction of the atoms occupy th e same quantum state, confirming thus a prediction made by Einstein 75 year s ago. The discovery of these atomic condensates has allowed for a precise check of theoretical models initially developed to account for the superflu idity of cold liquid Helium. It opens the way to coherent atomic sources, w hich are the equivalent, for matter waves, of the maser and laser sources f or electromagnetic waves.