Wave packet echoes in the motion of trapped atoms

We experimentally demonstrate and systematically study the stimulated reviv al (echo) of motional wave packet oscillations. For this purpose, we prepar e wave packets in an optical lattice by nonadiabatically shifting the poten tial and stimulate their reoccurrence by a second shift after a variable ti me delay. This technique, analogous to spin echoes, enables one even in the presence of strong dephasing to determine the coherence time of the wave p ackets. We find that for strongly bound atoms it is comparable to the cooli ng time and much longer than the inverse of the photon scattering rate.