Device-independent verification of Einstein–Podolsky–Rosen steering

Entanglement lies at the heart of quantum mechanics, and has been identified as an essential resource for diverse applications in quantum information. If entanglement could be verified without any trust in the devices of observers, i.e., in a device-independent (DI) way, then high security could be guaranteed for various quantum information processing tasks. In this work, we propose and experimentally demonstrate a DI protocol to certify the presence of entanglement based on Einstein–Podolsky–Rosen (EPR) steering. We first establish the DI verification framework by taking advantage of a measurement-device-independent technique and self-testing, which is able to verify all bipartite EPR-steerable states. In the scenario of three-measurement settings per party, the protocol is robust in tolerance of inefficient measurements and imperfect self-testing. Moreover, a four-photon experiment is implemented for verification beyond Bell nonlocal states. Our work enables further insight into quantum physics and could facilitate realistic implementation of secure quantum information processing tasks.