Experimental demonstration of intensity-modulation/direct-detection secret key distribution
Naoki Yamamori, Kyo Inoue
Abstract
Abstract Quantum key distribution, that transmits single-photons or strongly attenuated coherent light, has been studied for secret-key cryptography. This paper experimentally demonstrates a novel key distribution scheme, where a transmitter sends slightly intensity-modulated light with a power level used in conventional fiber communication systems and a receiver directly detects it with a conventional photodiode followed by threshold processing. Its security relies on that the slight intensity modulation is masked by quantum noise. Experiments are presented, which demonstrate that such slight modulation is feasible in practice and a secret key is actually created. The present key distribution scheme employs a setup similar to that in conventional optical communication, featuring practicality.