Suppression of dephasing of optically trapped atoms -: art. no. 013405

The decay in the hyperfine coherence of optically trapped atoms due to interactions with the environment, is only partly suppressed by echo spectroscopy [ M. F. Andersen Phys. Rev. Lett. 90, 023001 (2003) ], primarily due to dynamical (time-dependent) dephasing mechanisms. We demonstrate here an improved pulse sequence, for which the decay of coherence is reduced by a factor of 2.5 beyond the reduction offered by the echo spectroscopy. This reduction occurs when each dark period in-between pulses is shorter than the time scale over which substantial dephasing develops. The coherence time is then limited by mixing to other vibrational levels in the trap and, to a lesser extent, the lifetime of the internal states of the atoms.