Study On Sagnac Loop Time-division Phase-modulated Quantum Encoding

With the advent of the information age,the information safety has gained more and more attention,and considering the daily communication becoming more frequent,how to make the information be absolute security is a difficulty.Quantum key distribution(QKD)protocol with one-time-pad method help people solve this problem once and away,and up to now,phase-encoding and polarization-encoding scheme become hot issue within so much proposed quantum-coding scheme.In this paper,we proposed a Sagnac interferometer based scheme to realize the phase-encoding and polarization-encoding process,and demonstrated the feasibility with experiments.We can conclude from the analysis and experimental result that the new scheme could complete the quantum-encoding effectively and overcome the shortcomings.In the phase-encoding experiment,by using Sagnac time-division modulation in the plug&play protocol,the new scheme realized a more stable modulation and an increased contrast while the limitation of speed was optimized.We also completed the 100-MHz phase-encoding process and achieved 20-kHz sifted key rate in 12 hours with 5%QBER.In addition,we applied the Sagnac time-division modulation in polarization-encoding scheme.The principle was analyzed and demonstrated the feasibility for 1.25-GHz polarization encoding by experiment.The new scheme used single light source,and this could be effective to avoid attack aimed at different character of light source.