Manipulating the motion of a single atom in a standing wave via feedback

A standing light wave appears to a highly detuned two-level atom as a sinusoidal potential. This causes the atoms to be channeled to the minima of the potentials. At the same time, the atom changes the phase of the light field. Detecting this phase shift yields information about the position of the atom. In this paper we show that this information may be used to control the intensity of the light field so as to modify the effective shape of the potential ``seen'' by the atom. Our numerical simulations show that the effectiveness of the channeling may be significantly enhanced by such quantum-limited feedback. We discuss possible applications to atom lithography.