Stopping and storing light coherently

We present a general analysis for the criteria to stop and store light coherently. We show that a light pulse can be stopped in any physical system, provided that (i) the system bandwidth can be compressed to zero; (ii) the system has sufficient degrees of freedom to accommodate the pulse, and the bandwidth compression occurs while the pulse is in the system; and (iii) the bandwidth compression is done reversibly in an adiabatic fashion that preserves the phase space and the information in the original photon pulse during the entire duration of the stopping process. Based upon this general criterion, we present a brief discussion of stopping-light schemes using atomic resonances, and a detailed analysis of the all-optical scheme that we recently proposed. We show that the all-optical scheme can achieve arbitrarily small group velocities for large bandwidth pulses, and opens up new opportunities in both fundamental sciences and technological applications.