Oral/9. Quantum Optics and Quantum Information Technology

Tsinghua University;Tsinghua University;Tsinghua University;Tsinghua University

A dispersive optics quantum key distribution (DO-QKD) utilizing a quantum light source based on spontaneous four wave mixing (SFWM) in a piece of silicon waveguide is demonstrated. In DO-QKD schemes, the conjugate bases based on large group-velocity delay (GVD) of normal dispersion (ND) and anomalous dispersion (AD) modules are utilized for security test, which has already been proved to be secure against collective attacks. In Alice and Bob, photons are detected by these two bases randomly. Experimental results tell that the coincidence show excellent correlation when the photons are detected at Alice and Bob by the same bases. If not, the correlation would be degraded. By further measuring the covariance matrix associated with the correlation between Alice and Bob’s detection events, we can bound the information accessible to Eve. Any information that Alice and Bob share in excess of this bound will be secure. For key generation, we bin the single photon events in Alice and Bob in large alphabet way to get high-dimension information from each coincidence. By optimization towards detection events, the bit error rate (BER) due to the jitter of the detector electronics can be reduced to ~1.7%. At last, combined with the large alphabet time encoding and DO-QKD, a raw key rate of 50 kbps with 1.7% BER was achieved with an alphabet size of 4 and a bin width of 65 ps through optical fibers of 20 km, showing that silicon based quantum light sources have great potential on long distance QKD over optical fibers.