Josephson-type oscillations of a driven Bose-Einstein condensate in an optical lattice

Coherent transport behaviour has been demonstrated in experiments on atomic Bose-Einstein condensates driven by an external force through a quasi one- dimensional optical lattice. We exploit the Wannier-function representation of band states to elucidate the relationship of such coherent transport wi th the weak-link Josephson effect and test the observability of multimode b ehaviour in condensates by numerical solution of the Gross-Pitaevskii equat ion.