Improving the maximum transmission distance of four-state continuous-variable quantum key distribution by using a noiseless linear amplifier
Bingjie Xu, Chunming Tang, Hui Chen, Wenzheng Zhang, Fu-Chen Zhu · Physical Review A · 2013
A modified four-state CVQKD protocol is proposed to increase the maximum transmission distance and tolerable excess noise in the presence of Gaussian lossy and noisy channel by using a noiseless linear amplifier (NLA). An ideal NLA with gain $g$ can increase the maximum admission losses by $20{\mathrm{log}}_{10}g$ dB. Further, the imperfections in a practical NLA, such as the finite detection efficiency and imperfect single-photon source, are included in consideration.