Soft-Decision Decoding Error Probability Bounds for OFDM/QAM
Leonard E. Miller
We have implemented a quantum key distribution (QKD) system with polarization encoding at 850 nm over 1 km of optical fiber. The high-speed management of the bit-stream, generation of random numbers and processing of the sifting algorithm are all handled by a pair of custom data handling circuit boards. As a complete system using a clock rate of 1.25 Gbit/s, it produces sifted keys at a rate of 1.1 Mb/s with an error rate lower than 1.3% while operating at a transmission rate of 312.5 Mbit/s and a mean photon number 5 = 0.1. With a number of proposed improvements this system has a potential for a higher key rate without an elevated error rate.