Controlling excess noise in fiber-optics continuous-variable quantum key distribution
Jérôme Lodewyck, Thierry Debuisschert, Rosa Tualle-Brouri, Philippe Grangier · Physical Review A · 2005
We describe a continuous-variable coherent-states quantum-key distribution system working at $1550\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, and entirely made of standard fiber optics and telecommunications components, such as integrated-optics modulators, couplers and fast InGaAs photodiodes. The setup is composed of an emitter randomly modulating a coherent state in the complex plane with a doubly Gaussian distribution, and a receiver based on a shot-noise limited time-resolved homodyne detector. By using a reverse reconciliation protocol, the device can transfer a raw key rate up to $1\phantom{\rule{0.3em}{0ex}}\mathrm{Mbit}∕\mathrm{s}$, with a proven security against Gaussian or non-Gaussian attacks. The dependence of the secret information rate of the present fiber setup is studied as a function of the line transmission and excess noise.