Dynamical localization of atomic de Broglie waves: The influence of spontaneous emission

The quantized center-of-mass dynamics of two-level atoms in a periodically modulated standing-wave laser field is analyzed, including the decohering effect of spontaneous emission. Under conditions appropriate for the occurrence of dynamical localization as determined in previous work, we predict a random diffusive motion of dynamically localized de Broglie waves due to spontaneous emission and calculate the diffusion constant and the diffusing distribution of wave packets.