Improving the performance of the four-state continuous-variable quantum key distribution by using optical amplifiers

Abstract

We propose a method to improve the secret key rates of four-state continuous-variable quantum key distribution by using an optical preamplifier. The modified protocol allows the distribution of higher secret key rates over long distances. Included in this paper is a detailed investigation of the effects of inserting an optical parametric amplifier into the output of the quantum channel in the four-state protocol, which will be instructive and meaningful about the usage of amplifiers in order to achieve the optimal performance of the protocol in a specific scenario.