Anomalous dynamics of a single ion in an optical lattice

We have investigated the dynamics of a single ion in a one-dimensional optical lattice by tracing its position through fluorescent photons. A Mg-24(+) ion was radially confined in a two-dimensional radio-frequency trap, while an optical lattice superimposed on a weak electric potential was applied along the free axis. By decreasing the optical potential depth, a change of the transport characteristics from diffusive to quasiballistic was observed. Corresponding to this change, the distribution of the ion position showed an excess fluctuation reminiscent of Levy walks. A statistical analysis of these fluctuations confirmed a significant deviation from the Gaussian diffusion law.