A three‐dimensional Brownian motor, realised with symmetric optical lattices

A three‐dimensional Brownian motor is realised using lasercooled caesium atoms trapped in a system of two static, and individually symmetric, optical lattices; a so‐called double optical lattice. Isotropic fluctuations, emanating from light scattering, are rectified, and the diffusion of the ensemble of atoms is biased, with a resulting constant velocity that is controllable both in direction and magnitude. The working principle of the Brownian motor can be seen as a pulsation between two different potentials, both symmetric but around different points. The correlation between interferometric spatial offsets, and imbalance in optical pumping rates, leads to a spatio‐temporal asymmetry sufficient for generating a controlled, directed motion (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)