Efficient state transfer in an ultracold dense gas of heteronuclear molecules.

Polar molecules have bright prospects for novel quantum gases with long-range and anisotropic interactions, and could find uses in quantum information science and in precision measurements. However, high-density clouds of ultracold polar molecules have so far not been produced. Here, we report a key step towards this goal. We start from an ultracold dense gas of loosely bound ⁴⁰K⁸⁷Rb Feshbach molecules with typical binding energies of a few hundred kilohertz, and coherently transfer these molecules in a single transfer step into a vibrational level of the ground-state molecular potential bound by more than 10 GHz. Starting with a single initial state prepared with Feshbach association, we achieve a transfer efficiency of 84%. Given favourable Franck–Condon factors, the presented technique can be extended to access much more deeply bound vibrational levels and those exhibiting a significant dipole moment. [ABSTRACT FROM AUTHOR]