Excited-state-induced decoherence in long-lived Bloch oscillation

Abstract

Long-lived Bloch oscillation (BO) of the macroscopic wavefunction for a Bose–Einstein condensate in a tilted far-off resonant optical lattice has been exploited for precision measurement. The self-interaction between the ground state atoms is one main dephasing factor. When the self-interaction is effectively reduced to nearly zero by Feshbach resonance, experiments show that the long-lived BO can be achieved; however, after several seconds, the decoherence, not expected by conventional theory, can be induced. In this paper, we show that in this situation, the cross-interaction between atoms in the excited state and ground state becomes an important decoherence factor. Our numerical results show that for a short interrogation time, the cross-interaction has little influence on the BO, whereas, after a few seconds, the cross-interaction plays an important role of deteriorating BO. The Gross–Pitaevskii equation including the influence of excited atoms has been developed, giving much improved description of the long-lived BO dynamics.