Laser Cooling of Optically Trapped Molecules

June 28, 2018

Fig 1. Schematic of experimental apparatus and level diagram for sub-Doppler cooling of CaF.

Ultracold molecules are ideal platforms for many important applications, ranging from quantum simulation and quantum information processing to precision tests of fundamental physics. Producing trapped, dense samples of ultracold molecules is a challenging task. One promising approach is direct laser cooling, which can be applied to several classes of molecules not easily assembled from ultracold atoms. In a recent Letter to Natuer Physics, a group of physicists from the Harvard-MIT Center for Ultracold Atoms reported the production of trapped samples of laser-cooled CaF molecules with densities of 8 × 107 cm−3 and at phase-space densities of 2 × 10−9, 35 times higher than for sub-Doppler-cooled samples in free space. These advances were made possible by efficient laser cooling of optically trapped molecules to well below the Doppler limit, a key step towards many future applications, from ultracold chemistry to quantum simulation, where conservative trapping of cold and dense samples is desirable. In addition, the ability to cool optically trapped molecules opens up new paths towards quantum degeneracy.

See Loïc Anderegg, Benjamin L. Augenbraun, Yicheng Bao, Sean Burchesky, Lawrence W. Cheuk, Wolfgang Ketterle & John M. Doyle, "Laser cooling of optically trapped molecules," Nature Physics (2018) doi: https://doi.org/10.1038/s41567-018-0191-z.