Characterizing potentials by a generalized Boltzmann factor.

Based on the concept of a nonequilibrium steady state, we present a method to experimentally determine energy landscapes acting on colloidal systems. By measuring the stationary probability distribution and the current in the system, we explore potential landscapes with barriers up to several hundred k_BT. As an illustration, we use this approach to measure the effective diffusion coefficient of a colloidal particle moving in a tilted potential.