Analysis on the key-distribution efficiency of practical QKD system based on the way selecting bases using optical splitter

Analyze the key-distribution efficiency of practical the quantum key distribution (QKD) system selecting bases by optical splitter, propose the formula for the efficiency of effective detection relative to the average photon number, coefficient of light-path-loss, efficiency of detector, dark-count ratio, further obtain the maximum detection efficiency. Results of the analysis for the practical example show that optical splitter can realize switch function when average photon number is smaller than 1.