Quantum Gas of Deeply Bound Ground State Molecules

TL;DR

This paper reports the creation of an ultracold quantum gas of ground state molecules with high transfer efficiency, demonstrating coherent transfer and paving the way for molecular Bose-Einstein condensates in their ground state.

Contribution

It introduces a method for coherently transferring Feshbach molecules into deeply bound ground states with high efficiency, enabling new quantum gas experiments.

Findings

Transfer efficiency exceeds 80%

Coherence of transfer confirmed by Ramsey experiment

Molecular sample remains unheated during transfer

Abstract

We create an ultracold dense quantum gas of ground state molecules bound by more than 1000 wavenumbers by stimulated two-photon transfer of molecules associated on a Feshbach resonance from a Bose-Einstein condensate of cesium atoms. The transfer efficiency exceeds 80%. In the process, the initial loose, long-range electrostatic bond of the Feshbach molecule is coherently transformed into a tight chemical bond. We demonstrate coherence of the transfer in a Ramsey-type experiment and show that the molecular sample is not heated during the transfer. Our results show that the preparation of a quantum gas of molecules in arbitrary rovibrational states is possible and that the creation of a Bose-Einstein condensate of molecules in their rovibronic ground state is within reach.