时 间: 2010年9月16日（周四）上午10:30

地 点: 清华大学高等研究院 科学馆213报告厅

题 目: Clock Shifts of Optical Transitions in Ultracold Atomic Gases

报 告 人: Zhenhua Yu 博士

报告摘要: The state of the art of the standard for time is given by atomic clocks. The new generation of atomic clocks make use of the optical transitions of identical fermionic atoms loaded in optical lattices. In such systems, the resonant frequency shifts due to the interatomic interactions and the recoiling of atoms are expected to be strongly suppressed. However, in recent experiments of Campbell et al. [Science 324, 360 (2009)], when the fractional precision reaches the level of 1 × 10−16, frequency shifts given rise by the interactions are observed. To study the time evolution of the atomic clocks, we introduce a pseudospin formalism describing the density matrix of atoms. We derive a Bloch equation for the pseudospins which incorporates both spatial dependence of the probe laser field and interatomic interactions. We show that the interaction effects on the frequency shift are introduced in by the spatial inhomogeneity of the probe laser during the process of probe. In the low temperature semiclassical regime, we find that the magnitude of the shift is proportional to the temperature.