A High-Performance Continuous-Variable Long-Distance Protocol with KLM-Based Teleamplifier

Abstract

In continuous-variable quantum communication, probabilistic noiseless linear amplifiers serve as an essential error-correction strategy for overcoming transmission losses. The Knill-Laflamme-Milburn-based (KLM-based) teleamplifier, proposed in 2024, is the first to achieve the theoretical upper bound of success probability for this class of amplifiers. In this work, the KLM-based teleamplifier is incorporated into our proposed quantum repeater scheme to enhance its practicality. For comparison, several representative amplifier approaches are employed to replace the KLM-based teleamplifier, and their corresponding performance is investigated. Simulation results show that, compared with other schemes, the KLM-based scheme exhibits higher success probability, logarithmic negativity, and secret key rate under collective attack for both single- and multi-node repeater configurations. Moreover, the performance superiority of the scheme focuses on different performance metrics across various parameter regimes. As the first application of the KLM-based teleamplifier in a quantum communication protocol, our results demonstrate that: in addition to external techniques such as multiplexing, optimizing the internal amplifier module can also significantly improve the practicality of quantum repeater schemes, paving the way for future long-distance quantum communication.