Free-space quantum key distribution in urban daylight with the SPGD algorithm control of a deformable mirror
Yun-Hong Gong, Kui-Xing Yang, Hai-Lin Yong, Jian-Yu Guan, Guo-Liang Shentu, Chang Liu, Fengzhi Li, Yuan Wen Cao, Juan Yin, Sheng‐Kai Liao, Ji-Gang Ren, Qiang Zhang, Cheng-Zhi Peng, Jian-Wei Pan · Optics Express · 2018
Free-space quantum key distribution (QKD) is important to realize a global-scale quantum communication network. However, performing QKD in daylight against the strong background light noise is a major challenge. Here, we develop the stochastic parallel gradient descent (SPGD) algorithm with a deformable mirror to improve the signal-to-noise ratio (SNR). We then experimentally demonstrate free-space QKD in the presence of urban daylight. The final secure key rate of the QKD is 98∼419 bps throughout the majority of the daylight hours.