  We study the effect of a strong, oscillating driving field on the dynamics of
ultracold bosons held in an optical lattice. Modeling the system as a
Bose-Hubbard model, we show how the driving field can be used to produce and
maintain a coherent atomic current by controlling the phase of the intersite
tunneling processes. We investigate both the stroboscopic and time-averaged
behavior using Floquet theory, and demonstrate that this procedure provides a
stable and precise method of controlling coherent quantum systems.
