Rotating curved spacetime signatures from a giant quantum vortex.

Abstract

Gravity simulators¹ are laboratory systems in which small excitations such as sound² or surface waves^3,4 behave as fields propagating on a curved spacetime geometry. The analogy between gravity and fluids requires vanishing viscosity^2-4, a feature naturally realized in superfluids such as liquid helium or cold atomic clouds^5-8. Such systems have been successful in verifying key predictions of quantum field theory in curved spacetime^7-11. In particular, quantum simulations of rotating curved spacetimes indicative of astrophysical black holes require the realization of an extensive vortex flow¹² in superfluid systems. Here we demonstrate that, despite the inherent instability of multiply quantized vortices^13,14, a stationary giant quantum vortex can be stabilized in superfluid ⁴He. Its compact core carries thousands of circulation quanta, prevailing over current limitations in other physical systems such as magnons⁵, atomic clouds^6,7 and polaritons^15,16. We introduce a minimally invasive way to characterize the vortex flow^17,18 by exploiting the interaction of micrometre-scale waves on the superfluid interface with the background velocity field. Intricate wave-vortex interactions, including the detection of bound states and distinctive analogue black hole ringdown signatures, have been observed. These results open new avenues to explore quantum-to-classical vortex transitions and use superfluid helium as a finite-temperature quantum field theory simulator for rotating curved spacetimes¹⁹.