Quantum simulation of Unruh radiation

The exploration of quantum phenomena in a curved spacetime is an emerging interdisciplinary area at the interface between general relativity1–4, thermodynamics4–6 and quantum information7,8. One famous prediction in this field is Unruh thermal radiation3—the manifestation of thermal radiation from a Minkowski vacuum when viewed in an accelerating reference frame. Here, we report the experimental observation of a matter field with thermal fluctuations that agree with Unruh’s predictions. The matter field is generated within a framework for the simulation of quantum physics in a non-inertial frame, based on Bose–Einstein condensates that are parametrically modulated9 to make their evolution replicate the frame transformation. We further observe long-range phase coherence and temporal reversal of the matter-wave radiation, hallmarks that distinguish Unruh radiation from its classical counterpart. Our demonstration offers a new avenue for the investigation of the dynamics of quantum many-body systems in a curved spacetime.