Experimental characterisation of nonlocal photon superfluids

TL;DR

This paper demonstrates that laser light in thermo-optical media can serve as a room-temperature quantum fluid platform, enabling the study of many-body physics and superfluidity with simpler technology than atomic systems.

Contribution

It introduces a hydrodynamical approach to characterize photon superfluids in thermo-optical media and applies oceanography techniques for direct dispersion relation measurements.

Findings

Direct measurement of elementary excitations' dispersion relation.

Observation of superfluid signatures in photon fluid.

Validation of thermo-optical media as a quantum many-body system.

Abstract

Quantum gases of atoms and exciton-polaritons are nowadays a well established theoretical and experimental tool for fundamental studies of quantum many-body physics and suggest promising applications to quantum computing. Given their technological complexity, it is of paramount interest to devise other systems where such quantum many-body physics can be investigated at a lesser technological expense. Here we examine a relatively well-known system of laser light propagating through thermo-optical defocusing media: based on a hydrodynamical description of light as a quantum fluid of interacting photons, we investigate such systems as a valid, room temperature alternative to atomic or exciton-polariton condensates for studies of many-body physics. First, we show that by using a technique traditionally used in oceanography, it is possible to perform a direct measurement of the single-particle part of the dispersion relation of the elementary excitations on top of the photon fluid and to detect its global flow. Then, using a pump-and-probe set-up, we investigate the collective nature of low-wavevector sound modes of the fluid and observe signatures of superfluid behaviour.