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Dr. Wenyuan Wang

Fully Passive Quantum Key Distribution

The authors have proposed a Quantum Key Distribution (QKD) scheme without any modulators, which removes a major source of side channels on QKD sources. The proposal suggests a new type of passive linear optical QKD source. This breakthrough can help improve the security of practical QKD systems.

Publication Date: May 31, 2023

Authors: Wenyuan Wang, Rong Wang, Chengqiu Hu, Victor Zapatero, Li Qian (CQIQC member), Bing Qi, Marcos Curty, and Hoi-Kwong Lo (CQIQC Member).


We propose a fully passive linear optical quantum key distribution (QKD) source that implements both random decoy-state and encoding choices with postselection only, thus eliminating all side channels in active modulators. Our source is general purpose and can be used in, e.g., BB84, the six-state protocol, and reference-frame-independent QKD. It can even potentially be combined with measurement-device- independent QKD to achieve robustness against side channels in both detectors and modulators. We also perform a proof-of-principle experimental source characterization to show its feasibility.

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