Quantum self-testing is a device-independent way to certify quantum states and measurements using only the input-output statistics, with minimal assumptions about the quantum devices. Because of the high demand on tolerable noise, however, experimental self-testing was limited to two-photon systems. Here, we demonstrate the first robust self-testing for multi-photon genuinely entangled quantum states. We prepare two examples of four-photon graph states, the Greenberger-Horne-Zeilinger (GHZ) states with a fidelity of 0.957(2) and the linear cluster states with a fidelity of 0.945(2). Based on the observed input-output statistics, we certify the genuine four-photon entanglement and further estimate their qualities with respect to realistic noise in a device-independent manner.
@article{arxiv.2105.10298,
title = {Robust Self-Testing of Multiparticle Entanglement},
author = {Dian Wu and Qi Zhao and Xue-Mei Gu and Han-Sen Zhong and You Zhou and Li-Chao Peng and Jian Qin and Yi-Han Luo and Kai Chen and Li Li and Nai-Le Liu and Chao-Yang Lu and Jian-Wei Pan},
journal= {arXiv preprint arXiv:2105.10298},
year = {2021}
}