Analogue quantum simulation of the Hawking effect and black hole superradiance – HAWQ

Analogue quantum simulations enable the laboratory study of quantum field theories on curved spacetime via the equivalence between the kinematics of excitations in material systems and of massless quantum fields in astrophysics. For example, a giant vortex flow in quantum fluids allows to simulate field theories on rotating black hole spacetimes. The vortex flow forms an ergosurface and a horizon where its total and radial velocities equal the speed of sound, respectively. Phonons inside the ergosurface must co-rotate with the vortex, while they are trapped inside the horizon by the supersonic speed of the flow within. The annihilation and creation operators of the quantised acoustic field will mix at both surfaces, yielding spontaneous emission from the vacuum by the Hawking effect at the horizon, and by ‘rotational superradiance’ at the ergosurface. Emission from the horizon and from the ergosurface will mutually enhance each other, resulting in an exponential growth of field amplitudes between the two surfaces in a process known as the ‘black hole bomb’ – a dynamical instability of the spacetime.
So far, the Hawking effect has not been studied in rotating geometries and dynamical instabilities are difficult to study in the relativistic context. This raises interest for our methods to simulate otherwise inaccessible quantum field phenomena.
In HAWQ, we will experimentally and theoretically study the acoustic field on a controlled vortex flow and tune the interplay between the Hawking effect and superradiance to observe the dynamical instability, which manifests as a modification of the entanglement of Hawking pairs across the acoustic horizon. We will use a quantum fluid of microcavity polaritons whose flow may be controlled all- optically and whose properties (density, phase, motion of phonons within) can all be accessed via the light coming out of the cavity, enabling quantum optics methods like homodyne detection to measure entanglement.