JOSEPHSON EFFECT IN A BOSE-EINSTEIN CONDENSATE. Mark Kasevich and Brian Anderson at Yale have loaded a Bose-Einstein condensate of rubidium atoms (occupying a single quantum state) into the grip of an optical lattice, a series of energy wells established by the electric field of a laser beam. With the help of gravity, atoms from one part of the condensate can tunnel to another (spatially separated) part but retain their coherent relation to the rest of the condensate, analogous to the Josephson effect, in which part of a supercurrent can tunnel across an insulator from one superconductor to another. The spaced-out drops of atoms constitute a pulsed atom laser beam. (Science, 27 November 1998.)