Quantum Fluid Mimics Black Hole’s Horizon
Scientists predict that exotic quantum effects occur near a black hole’s event horizon—the boundary beyond which nothing can escape. These effects are unobservable with current astronomical detectors but can be explored using lab-based analogues of event horizons. Now Maxime Jacquet at the Kastler Brossel Laboratory in France and his colleagues have demonstrated a new analogue that uses a quantum fluid of light [1]. This platform offers a way to explore how quantum fields behave both near black holes and in arbitrary curved spacetimes.
The researchers directed a laser beam at a set of layered semiconductors sandwiched between two mirrors. The beam’s photons coupled to electron–hole bound states in the semiconductors, forming hybrid light–matter quasiparticles called polaritons. These quasiparticles collectively acted like a fluid of light that flowed within the semiconductors. By manipulating the beam’s spatial profile, the team created an artificial horizon where the flow speed transitioned from being slower than the speed of sound to being supersonic. Sound waves that naturally formed in this fluid could not escape from beyond the horizon, in analogy with a black hole’s horizon. Using a precise, light-based measurement technique, the team studied the behavior of sound waves on each side of the artificial horizon.
For a black hole, quantum fluctuations just outside the event horizon are thought to create pairs of particles in which one particle has negative energy and the other has positive energy. The former falls into the black hole, while the latter is emitted from it, and this process causes the black hole to gradually lose mass. The researchers found that their polariton fluid had the necessary ingredients for an equivalent effect, with sound waves rather than particles.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- K. Falque et al., “Polariton fluids as quantum field theory simulators on tailored curved spacetimes,” Phys. Rev. Lett. 135, 023401 (2025).