Momentum correlations of the Hawking effect in a quantum fluid

TL;DR

This paper investigates the momentum-space correlations of the Hawking effect in a quantum fluid, providing a new perspective that complements real-space studies and offers experimentally accessible signatures.

Contribution

It introduces a numerical momentum-space analysis of Hawking radiation in quantum fluids using the truncated Wigner approximation, applicable to various systems.

Findings

Identifies momentum-space signatures of Hawking radiation

Demonstrates the method's applicability to polaritonic fluids

Provides a diagnostic tool for experimental observation

Abstract

The Hawking effect -- the spontaneous emission of correlated quanta from horizons -- can be observed in laboratory systems where an acoustic horizon forms when a fluid transitions from subcritical to supercritical flow. Although most theoretical and experimental studies have relied on real-space observables, the frequency-dependent nature of the Hawking process motivates a momentum-space analysis to access its spectral structure and entanglement features. Here, we numerically compute the momentum-space two-point correlation function in a quantum fluid using the truncated Wigner approximation, a general method applicable to both conservative and driven-dissipative systems. We consider a polaritonic fluid of light in a realistic configuration known to yield strong real-space correlations between Hawking, partner, and witness modes. We find signatures that are directly accessible in state-of-the-art experiments and offer a robust diagnostic of spontaneous emission. Our results form the basis for a new theoretical framework to assess a variety of effects, such as quasi-normal mode emission or modifications of the horizon structure on the Hawking spectrum.