Measurement-Device-Independent Entanglement Witness of Tripartite Entangled States and Its Applications
Zheng-Da Li, Qi Zhao, Rui Zhang, Li-Zheng Liu, Xu-Fei Yin, Xingjian Zhang, Yue-Yang Fei, Kai Chen, Nai-Le Liu, Feihu Xu, Yu-Ao Chen, Li Li, Jian-Wei Pan · Physical Review Letters · 2020
Entanglement witness is of great importance in characterizing quantum systems. The imperfections in conventional entanglement witness schemes could lead to the misidentification of a separated state as an entangled state. Measurement-device-independent entanglement witness (MDIEW) has been proposed and demonstrated to resolve the imperfect measurement devices. So far, however, the MDIEW has been restricted to a two-party qubit entangled state. Here, for the first time, we demonstrate MDIEW for multipartite entangled states. We experimentally detect the genuine entanglement and the entanglement structure of a tripartite entangled state based on an eight-photon interferometry. Furthermore, with the verified multipartite entangled state, we demonstrate quantum randomness generation and open-destination quantum key distribution in an measurement-device-independent manner. Our research presents an important step toward building a robust and secure quantum network.