Creation of a low-entropy quantum gas of polar molecules in an optical lattice

TL;DR

This paper demonstrates the creation of a low-entropy quantum gas of polar molecules in an optical lattice, enabling advanced studies of many-body quantum phenomena with long-range interactions.

Contribution

It introduces a method to synthesize low-entropy polar molecules in an optical lattice from ultracold atomic gases, achieving a significant reduction in entropy per particle.

Findings

Achieved a molecular filling fraction of 25%

Reached an entropy as low as 2.2 k_B per molecule

Successfully created a low-entropy molecular quantum gas

Abstract

Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena such as quantum magnetism. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle has been an outstanding experimental challenge. In this paper, we report the synthesis of a low entropy molecular quantum gas by creating molecules at individual sites of a three-dimensional optical lattice that is initially loaded from a low entropy mixture of K and Rb quantum gases. We make use of the quantum statistics and interactions of the initial atom gases to load into the optical lattice, simultaneously and with good spatial overlap, a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magneto-association and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contained one Rb and one K atom. The achieved filling fraction of 25% indicates an entropy as low as $2.2\,k_B$ per molecule. This low-entropy molecular quantum gas opens the door to novel studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions.