Measuring pair correlations in Bose and Fermi gases via atom-resolved microscopy

TL;DR

This paper introduces a microscopy technique for directly observing and measuring interparticle correlations in continuum Bose and Fermi gases, revealing quantum phenomena like Bose-Einstein condensation, fermionic exchange holes, and fermion pairing.

Contribution

It demonstrates atom-resolved detection in continuum quantum gases, enabling direct measurement of correlations and pairing phenomena previously accessible mainly in lattice systems.

Findings

Observation of Bose-Einstein condensation with single-atom resolution

Measurement of two-particle $g^{(2)}$ correlations in thermal bosons and fermions

Direct imaging of non-local fermion pairs in the BEC-BCS crossover

Abstract

We demonstrate atom-resolved detection of itinerant bosonic $^{23}$Na and fermionic $^6$Li quantum gases, enabling the direct in situ measurement of interparticle correlations. In contrast to prior work on lattice-trapped gases, here we realize microscopy of quantum gases in the continuum. We reveal Bose-Einstein condensation with single-atom resolution, measure the enhancement of two-particle $g^{(2)}$ correlations of thermal bosons, and observe the suppression of $g^{(2)}$ for fermions; the Fermi or exchange hole. For strongly interacting Fermi gases confined to two dimensions, we directly observe non-local fermion pairs in the BEC-BCS crossover. We obtain the pairing gap, the pair size, and the short-range contact directly from the pair correlations. In situ thermometry is enabled via the fluctuation-dissipation theorem. Our technique opens the door to the atom-resolved study of strongly correlated quantum gases of bosons, fermions, and their mixtures.