Abstract
Gravity simulators(1) are laboratory systems in which small excitations such as sound(2) 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 flow(12) 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 (4)He. Its compact core carries thousands of circulation quanta, prevailing over current limitations in other physical systems such as magnons(5), 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 spacetimes(19).