Phys.org January 25, 2021
Measurement-device-independent quantum key distribution (MDI-QKD) protocol can help in closing all loopholes on detection at once. It has only been successfully implemented using fiber optics. To implement the protocol across free-space channels two main challenges need to be addressed. One is to reduce the gap between theory and practice of QKD, and the other one is to extend the distance of QKD. Researchers in China have developed a robust adaptive optics system – high-precision time synchronization and frequency locking between independent photon sources located far apart to realize free-space MDI-QKD over a 19.2-km urban atmospheric channel. The experiment takes the first step toward satellite-based MDI-QKD opening the way to quantum experiments in free space involving long-distance interference of independent single photons. Their long-term goal is to demonstrate satellite-based MDI-QKD and eventually to build a global quantum network…read more. TECHNICAL ARTICLE
A concept figure of the MDI-QKD experiment in a city. Telescopes are in high-rise buildings for transmitting encoded photons… Credit: Yao Zheng/Micius Salon.