Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science. 2017 Nov 24;358(6366):1078-1080. doi: 10.1126/science.aan5614.
Protocols for attaining quantum degeneracy in atomic gases almost exclusively rely on evaporative cooling, a time-consuming final step associated with substantial atom loss. We demonstrate direct laser cooling of a gas of rubidium-87 (Rb) atoms to quantum degeneracy. The method is fast and induces little atom loss. The atoms are trapped in a two-dimensional optical lattice that enables cycles of compression to increase the density, followed by Raman sideband cooling to decrease the temperature. From a starting number of 2000 atoms, 1400 atoms reach quantum degeneracy in 300 milliseconds, as confirmed by a bimodal velocity distribution. The method should be broadly applicable to many bosonic and fermionic species and to systems where evaporative cooling is not possible.
实现原子气体量子简并的方案几乎完全依赖于耗散冷却，这是一个耗时的最终步骤，伴随着大量原子损失。我们展示了铷-87（Rb）原子气体的直接激光冷却达到量子简并。该方法快速且原子损失小。原子被囚禁在二维光晶格中，使得压缩循环能够增加密度，然后进行拉曼边带冷却以降低温度。从最初的 2000 个原子开始，在 300 毫秒内有 1400 个原子达到量子简并，这一点通过双模态速度分布得到了证实。该方法应该广泛适用于许多玻色子和费米子物种，以及那些不能进行耗散冷却的系统。
