A phase microscope for quantum gases

TL;DR

This paper introduces a novel phase microscope technique to study coherence properties of ultracold Bose gases in optical lattices, revealing phase correlations and fluctuations across the thermal phase transition.

Contribution

It presents a new phase microscopy method based on site-resolved phase fluctuation mapping, enabling detailed study of coherence in quantum gases.

Findings

Observed algebraic decay of phase correlations in superfluid phase

Detected linear temperature dependence of phase correlation exponent

Demonstrated technique's potential for studying strongly-correlated systems

Abstract

Coherence properties are central to quantum systems and are at the heart of phenomena such as superconductivity. Here we study coherence properties of an ultracold Bose gas in a two-dimensional optical lattice across the thermal phase transition. To infer the phase coherence and phase fluctuation profile, we use direct matter-wave imaging of higher Talbot revivals as well as a new phase microscope based on a site-resolved mapping of phase fluctuations to density fluctuations during matter-wave imaging. We observe the algebraic decay of the phase correlations in the superfluid phase and a linear temperature increase of the exponent. These techniques will also allow studying coherence properties in strongly-correlated quantum systems with full spatial resolution.