Entangled Hawking radiation emitted by an analogue black hole has been observed by a physicist in Israel. The experiment simulates the event horizon of a black hole using sound propagation in a Bose–Einstein condensate (BEC). The measurement shows that, if Einstein’s general theory of relativity holds at the boundary of a black hole, then black holes must emit radiation.
Ref: Observation of quantum Hawking radiation and its entanglement in an analogue black hole. Nature Physics (15 August 2016) | DOI: 10.1038/nphys3863
We observe spontaneous Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole in an atomic Bose–Einstein condensate. Correlations are observed between the Hawking particles outside the black hole and the partner particles inside. These correlations indicate an approximately thermal distribution of Hawking radiation. We find that the high-energy pairs are entangled, while the low-energy pairs are not, within the reasonable assumption that excitations with different frequencies are not correlated. The entanglement verifies the quantum nature of the Hawking radiation. The results are consistent with a driven oscillation experiment and a numerical simulation.