Biography
Yu-Huai Li is an Associate Professor at the University of Science and Technology of China (USTC), where he earned his Ph.D. in Physics in 2017. His research focuses on quantum entanglement, quantum communication, large-scale quantum optical interference in free space, and quantum computation. His work was awarded the Newcomb Cleveland Prize from the American Association for the Advancement of Science (AAAS) and was selected as one of the Physics World Top Ten Breakthroughs of the Year.
Abstract
Twin-field quantum key distribution (TF-QKD) elevates the secure key rate from a linear to a square-root dependence on channel loss while preserving measurement-device-independent security. This protocol is uniquely positioned to enable global-scale quantum networks, even under extreme channel loss. While fiber-based TF-QKD implementations have advanced rapidly since its proposal, free-space realizations have remained elusive due to atmospheric turbulence-induced phase distortions. Here, we report the first experimental demonstration of free-space TF-QKD over 14.2 km urban atmospheric channels, surpassing the effective atmospheric thickness – a critical threshold for satellite compatibility. We achieve a secret key rate exceeding the repeaterless capacity bound, a milestone for practical quantum communication. Our approach eliminates the need for an auxiliary channel to stabilize a closed interferometer, instead leveraging open-channel time and phase control of optical pulses. This work represents a pivotal advance toward satellite-based global quantum networks, combining high-speed key distribution with inherent resistance to real-world channel fluctuations.