Characterization of State-Preparation Uncertainty in Quantum Key Distribution
Anqi Huang, Akihiro Mizutani, Hoi‐Kwong Lo, Vadim Makarov, Kiyoshi Tamaki
Abstract
To achieve secure quantum key distribution, all imperfections in the source unit must be incorporated in a security proof and measured in the lab. Here we perform a proof-of-principle demonstration of the experimental techniques for characterizing the source phase and intensity fluctuation in commercial quantum key distribution systems. When we apply the measured phase-fluctuation intervals to the security proof that takes into account fluctuations in the state preparation, it predicts a key distribution distance of over $100\phantom{\rule{0.2em}{0ex}}\mathrm{km}$ of fiber. The measured intensity fluctuation intervals are, however, so large that the proof predicts zero key, indicating a source improvement may be needed. Our characterization methods pave the way for a future certification standard.