近日，德国汉诺威大学的Fei Ding及其研究团队取得一项新进展。经过不懈努力，他们利用一个半导体单光子源实现高速城际量子密钥分发。相关研究成果已于2024年7月2日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队报道了第一个使用明亮确定性单光子源的城际QKD实验。研究人员利用嵌入在圆形布拉格光栅结构中的半导体量子点发射的电信C波段高速率单光子，实现了基于偏振编码的BB84协议。研究人员利用德国汉诺威和布伦瑞克之间长达79公里的链路，损耗25.49dB(相当于130公里的直接连接光纤)，证明了每脉冲4.8×10^-5的创纪录高密钥比特，平均量子比特误码率约为0.65%。发现了28.11dB的渐近最大可容忍损耗，对应于144公里长的标准电信光纤。因此，确定性半导体源挑战了最先进的QKD协议，并有潜力在测量器件独立协议和量子中继器应用中脱颖而出。

据悉，量子密钥分发(QKD)使信息传输安全，不受窃听者的常规攻击。在QKD协议中使用按需量子光源有望帮助提高安全性和最大可容忍损耗。半导体量子点(QDs)由于具有高亮度和低多光子贡献的单光子确定性发射而成为量子通信应用的重要组成部分。

附：英文原文

Title: High-rate intercity quantum key distribution with a semiconductor single-photon source

Author: Yang, Jingzhong, Jiang, Zenghui, Benthin, Frederik, Hanel, Joscha, Fandrich, Tom, Joos, Raphael, Bauer, Stephanie, Kolatschek, Sascha, Hreibi, Ali, Rugeramigabo, Eddy Patrick, Jetter, Michael, Portalupi, Simone Luca, Zopf, Michael, Michler, Peter, Kck, Stefan, Ding, Fei

Issue&Volume: 2024-07-02

Abstract: Quantum key distribution (QKD) enables the transmission of information that is secure against general attacks by eavesdroppers. The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss. Semiconductor quantum dots (QDs) are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution. Here we report on the first intercity QKD experiment using a bright deterministic single photon source. A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure. Utilising the 79km long link with 25.49dB loss (equivalent to 130km for the direct-connected optical fibre) between the German cities of Hannover and Braunschweig, a record-high secret key bits per pulse of 4.8×10^-5 with an average quantum bit error ratio of~0.65% are demonstrated. An asymptotic maximum tolerable loss of 28.11dB is found, corresponding to a length of 144km of standard telecommunication fibre. Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.

DOI: 10.1038/s41377-024-01488-0

Source: https://www.nature.com/articles/s41377-024-01488-0