We report an experiment to test quantum interference, entanglement and nonlocality using two dissimilar photon sources, the Sun and a semiconductor quantum dot on the Earth, which are separated by 150 million kilometers. By making the otherwise vastly distinct photons indistinguishable all degrees of freedom, we observe time-resolved two-photon quantum interference with a raw visibility of 0.796(17), well above the 0.5 classical limit, providing the first evidence of quantum nature of thermal light. Further, using the photons with no common history, we demonstrate post-selected two-photon entanglement with a state fidelity of 0.826(24), and a violation of Bell's inequality by 2.20(6). The experiment can be further extended to a larger scale using photons from distant stars, and open a new route to quantum optics experiments at an astronomical scale.
@article{arxiv.1905.02868,
title = {Quantum interference between light sources separated by 150 million kilometers},
author = {Yu-Hao Deng and Hui Wang and Xing Ding and Z. -C. Duan and Jian Qin and M. -C. Chen and Yu He and Yu-Ming He and Jin-Peng Li and Yu-Huai Li and Li-Chao Peng and E. S. Matekole and Tim Byrnes and C. Schneider and M. Kamp and Da-Wei Wang and Jonathan P. Dowling and Sven Höfling and Chao-Yang Lu and Marlan O. Scully and Jian-Wei Pan},
journal= {arXiv preprint arXiv:1905.02868},
year = {2019}
}