Long-distance entanglement-based quantum key distribution over optical fiber
Toshimori Honjo, Sae Woo Nam, Hiroki Takesue, Q. Zhang, Hiroyuki Kamada, Y. Nishida, Osamu Tadanaga, Masaki Asobe, Burm Baek, Robert H. Hadfield, Shigehito Miki, Mikio Fujiwara, Masahide Sasaki, Zhixin Wang, Kyo Inoue, Y. Yamamoto · Optics Express · 2008
We report the first entanglement-based quantum key distribution (QKD) experiment over a 100-km optical fiber. We used superconducting single photon detectors based on NbN nanowires that provide high-speed single photon detection for the 1.5-mum telecom band, an efficient entangled photon pair source that consists of a fiber coupled periodically poled lithium niobate waveguide and ultra low loss filters, and planar lightwave circuit Mach-Zehnder interferometers (MZIs) with ultra stable operation. These characteristics enabled us to perform an entanglement-based QKD experiment over a 100-km optical fiber. In the experiment, which lasted approximately 8 hours, we successfully generated a 16 kbit sifted key with a quantum bit error rate of 6.9 % at a rate of 0.59 bits per second, from which we were able to distill a 3.9 kbit secure key.