Experimental Side-Channel-Free Quantum Key Distribution

Chi Zhang, 2, 3 Xiao-Long Hu, Jiu-Peng Chen, 2, 3 Yang Liu, 2, 3 Weijun Zhang, Zong-Wen Yu, 6 Hao Li, Lixing You, Zhen Wang, Xiang-Bin Wang, 3, 4 Qiang Zhang, 2 and Jian-Wei Pan 2 Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China Jinan Institute of Quantum Technology, Jinan, Shandong 250101, China State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China Data Communication Science and Technology Research Institute, Beijing 100191, China Abstract Quantum key distribution can provide unconditionally secure key exchange for remote users in theory. In practice, however, in most quantum key distribution systems, quantum hackers might steal the secure keys by listening to the side channels in the source, such as the photon frequency spectrum, emission time, propagation direction, spatial angular momentum, and so on. It is hard to prevent such kinds of attacks because side channels may exist in any of the encoding space whether the designers take care of or not. Here we report an experimental realization of a side-channel-free quantum key distribution protocol which is not only measurement-device-independent, but also immune to all side-channel attacks in the source. We achieve a secure key rate of 4.80× 10−7 per pulse through 50 km fiber spools.