Bose fireworks and Hawking-Unruh radiation

Quantum phenomenon in curved spacetimes is an intriguing research topic that aims to offer hints to the not-yet-known theory of quantum gravity. One famous prediction is the Hawking-Unruh effect, the manifestation of Minkowski vacuum in a reference frame with high acceleration. We simulate the transformation to an accelerating frame by parametrically driving a Bose-Einstein condensate of atoms. Above the critical threshold, the driven condensate suddenly emits many jets of matterwaves in all directions. The emission resembles fireworks and displays a Boltzmann distribution that resembles the Unruh radiation. The measured temperature and entropy are in excellent agreement with Unruh’s predictions. We further detect non-local quantum coherence and temporal reversibility of the matterwave emission, which are hallmarks that distinguish Unruh radiations from the classical blackbody radiation. Our results confirm the quantum nature of Unruh effect.