  For a colloidal particle driven by a constant force across a periodic
potential, we investigate the distribution of entropy production both
experimentally and theoretically. For short trajectories, the fluctuation
theorem holds experimentally. The mean entropy production rate shows two
regimes as a function of the applied force. Theoretically, both mean and
variance of the pronounced non-Gaussian distribution can be obtained from a
differential equation in good agreement with the experimental data.
