Roughness suppression via rapid current modulation on an atom chip

We present a method to suppress the roughness of the potential of a wire-based, magnetic atom guide: modulating the wire current at a few tens of kHz, the potential roughness, which is proportional to the wire current, averages to zero. Using ultracold Rb-87 clouds, we show experimentally that modulation reduces the roughness by at least a factor five without measurable heating or atom loss. This roughness suppression results in a dramatic reduction of the damping of center-of-mass oscillations.