Interferences between Bogoliubov excitations and their impact on the evidence of superfluidity in a paraxial fluid of light

TL;DR

This paper investigates the interference effects between Bogoliubov excitations in a paraxial fluid of light, demonstrating their significance for confirming superfluidity and advancing quantum simulation techniques with photons.

Contribution

It provides the first experimental observation of phonon interference effects in light superfluids, highlighting their impact on dispersion relation measurements.

Findings

Interference between counter-propagating Bogoliubov excitations observed.

Interferences significantly affect the measurement of the dispersion relation.

Results confirm a key signature of superfluidity in light.

Abstract

Paraxial fluids of light represent an alternative platform to atomic Bose-Einstein condensates and superfluid liquids for the study of the quantum behaviour of collective excitations. A key step in this direction is the precise characterization of the Bogoliubov dispersion relation, as recently shown in two experiments. However, the predicted interferences between the phonon excitations that would be a clear signature of the collective superfluid behaviour have not been observed to date. Here, by analytically, numerically, and experimentally exploring the phonon phase-velocity, we observe the presence of interferences between counter-propagating Bogoliubov excitations and demonstrate their critical impact on the measurement of the dispersion relation. These results are evidence of a key signature of light superfluidity and provide a novel characterization tool for quantum simulations with photons.