Long-distance continuous-variable quantum key distribution with feasible physical noiseless linear amplifiers

Noiseless linear amplifiers (NLAs) provide a powerful tool to achieve long-distance continuous-variable (CV) quantum key distribution (QKD) in the presence of realistic setups with nonunit reconciliation efficiency. We address a NLA-assisted CV QKD protocol implemented via realistic physical NLAs, namely, quantum scissors and single-photon catalysis, and compare their performance with respect to the ideal NLA gˆn. We investigate also the robustness of two schemes against inefficient conditional detection and discuss the two alternative scenarios in which the gain associated with the NLA is either fixed or optimized.