Squeezing Out the Entropy of Fermions in Optical Lattices

TL;DR

This paper proposes a method to significantly reduce the entropy of fermionic atoms in optical lattices by transferring entropy to a surrounding Bose-Einstein condensate, facilitating quantum emulation of complex electronic models.

Contribution

It introduces a novel entropy-squeezing technique that enables lower entropy states in fermionic gases, advancing quantum simulation capabilities.

Findings

Entropy per particle can be reduced to a few percent of current lowest values.

The method effectively transfers entropy from fermions to a BEC reservoir.

This approach could enable emulation of strongly correlated electronic systems at ultra-low temperatures.

Abstract

At present, there is considerable interest in using atomic fermions in optical lattices to emulate the mathematical models that have been used to study strongly correlated electronic systems. Some of these models, such as the two dimensional fermion Hubbard model, are notoriously difficult to solve, and their key properties remain controversial despite decades of studies. It is hoped that the emulation experiments will shed light on some of these long standing problems. A successful emulation, however, requires reaching temperatures as low as $10^{-12}$K and beyond, with entropy per particle far lower than what can be achieved today. Achieving such low entropy states is an essential step and a grand challenge of the whole emulation enterprise. In this paper, we point out a method to literally squeeze the entropy out from a Fermi gas into a surrounding Bose-Einstein condensed gas (BEC), which acts as a heat reservoir. This method allows one to reduce the entropy per particle of a lattice Fermi gas to a few percent of the lowest value obtainable today.