Free fermion antibunching in a degenerate atomic Fermi gas released from an optical lattice

TL;DR

This paper reports the first direct observation of antibunching in a degenerate atomic Fermi gas, revealing fundamental fermionic quantum correlations and enabling characterization of the system's ordering and temperature.

Contribution

It provides the first experimental evidence of fermionic antibunching in neutral atoms and demonstrates how atomic shot noise analysis can characterize quantum phases in optical lattices.

Findings

Observed antibunching in neutral fermionic atoms

Reduced correlations related to original lattice spacing

Characterized Fermi gas ordering and temperature

Abstract

Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the underlying particles. Whereas for bosonic particles the correlated noise observed for e.g. photons or bosonic neutral atoms can still be explained within a classical field description with fluctuating phases, the anticorrelations in the detection of fermionic particles have no classical analogue. The observation of such fermionic antibunching is so far scarce and has been confined to electrons and neutrons. Here we report on the first direct observation of antibunching of neutral fermionic atoms. Through an analysis of the atomic shot noise in a set of standard absorption images, of a gas of fermionic 40K atoms released from an optical lattice, we find reduced correlations for distances related to the original spacing of the trapped atoms. The detection of such quantum statistical correlations has allowed us to characterise the ordering and temperature of the Fermi gas in the lattice. Moreover, our findings are an important step towards revealing fundamental fermionic many-body quantum phases in periodic potentials, which are at the focus of current research.