Exploring the Quantum-to-Classical Vortex Flow: Quantum Field Theory Dynamics in Rotating Curved Spacetimes

Abstract

Gravity simulators [1] are laboratory systems where small excitations like sound [2] or surface waves [3] behave as fields propagating on a curved spacetime geometry. The analogy between gravity and fluids requires vanishing viscosity [2, 3], a feature naturally realised in superfluids like liquid helium or cold atomic clouds [4-6]. Such systems have been successful in verifying key predictions of quantum field theory in curved spacetime [6-9]. In particular, quantum simulations of rotating curved spacetimes indicative of astrophysical black holes require the realisation of an extensive vortex flow [10] in superfluid systems. Despite the inherent instability of multiply quantised vortices [11, 12], here we demonstrate that a stationary giant quantum vortex can be stabilised in superfluid 4He. Its compact core carries thousands of circulation quanta, prevailing over current limitations in other physical systems such as magnons [4], cold gases [5, 6] and polaritons [13, 14]. We introduce a minimally invasive way to characterise the vortex flow [15, 16] 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 utilise superfluid helium as a finite temperature quantum field theory simulator for rotating curved spacetimes [17].

Towards analogue black hole merger

“…In 1D, the fluid is usually injected at one edge of the system and removed at the other edge [10,13]. In 2D, the so-called "draining bathtub" configuration is used, with a local drain in the center [14,15]. Quantum fluids, such as atomic BECs (Bose-Einstein condensates), were rather considered in 1D, without losses, in a dynamical configuration with a moving potential [11,16].…”