The emergence of quantum mechanics and general relativity has transformed our understanding of the natural world significantly. However, integrating these two theories presents immense challenges, and their interplay remains untested. Recent theoretical studies suggest that the single-photon interference covering huge space can effectively probe the interface between quantum mechanics and general relativity. We developed an alternative design using unbalanced Michelson interferometers to address this and validated its feasibility over an 8.4 km free-space channel. Using a high-brightness single-photon source based on quantum dots, we demonstrated single-photon interference along this long-distance baseline. We achieved a phase measurement precision of 16.2 mrad, which satisfied the measurement requirements for a gravitational redshift at the geosynchronous orbit by five times the standard deviation. Our results confirm the feasibility of the single-photon version of the Colella-Overhauser-Werner experiment for testing the quantum effects in curved spacetime.
@article{arxiv.2408.03259,
title = {Single-photon interference over 8.4 km urban atmosphere: towards testing quantum effects in curved spacetime with photons},
author = {Hui-Nan Wu and Yu-Huai Li and Bo Li and Xiang You and Run-Ze Liu and Ji-Gang Ren and Juan Yin and Chao-Yang Lu and Yuan Cao and Cheng-Zhi Peng and Jian-Wei Pan},
journal= {arXiv preprint arXiv:2408.03259},
year = {2024}
}