Experimental realization of quantum walks near synthetic horizons on photonic lattices

Entanglement plays crucial roles in quantum optics, providing a prerequisite for these recent unprecedented leaps. Nevertheless, the study of quantum entanglement under the influence of relativity, an important ingredient of quantum optics, still needs to be explored. In parallel, integrated photonic chips, particularly those with the aid of transformation optics, have simulated various relativity phenomena including gravitational lensing and Unruh radiation. However, thus far, studying relativistic quantum optics on this type of platform has not yet occurred. Here, we propose and experimentally realize quantum walks of entangled photons near an emulated Rindler horizon. Remarkably, we find that quantum interference near the synthetic horizon leads to a counterintuitive phenomenon of optical escape. Our study paves the way to a tabletop platform for studying quantum phenomena in various relativistic space-time metrics, and may bring an implication for the test of quantum theory in relativity.