Zhou Kunlin, Wu Xuelin, Mao Yun, Chen Zhiya, Liao Qin, Guo Ying
School of Traffic and Transportation Engineering, Central South University, Changsha 410083, China.
Jiangsu Key Construction Laboratory of IoT Application Technology, Taihu University, Wuxi 214064, China.
Entropy (Basel). 2020 Aug 12;22(8):882. doi: 10.3390/e22080882.
In practical quantum communication networks, the scheme of continuous-variable quantum key distribution (CVQKD) faces a challenge that the entangled source is controlled by a malicious eavesdropper, and although it still can generate a positive key rate and security, its performance needs to be improved, especially in secret key rate and maximum transmission distance. In this paper, we proposed a method based on the four-state discrete modulation and a heralded hybrid linear amplifier to enhance the performance of CVQKD where the entangled source originates from malicious eavesdropper. The four-state CVQKD encodes information by nonorthogonal coherent states in phase space. It has better transmission distance than Gaussian modulation counterpart, especially at low signal-to-noise ratio (SNR). Moreover, the hybrid linear amplifier concatenates a deterministic linear amplifier (DLA) and a noiseless linear amplifier (NLA), which can improve the probability of amplification success and reduce the noise penalty caused by the measurement. Furthermore, the hybrid linear amplifier can raise the SNR of CVQKD and tune between two types of performance for high-gain mode and high noise-reduction mode, therefore it can extend the maximal transmission distance while the entangled source is untrusted.
在实际的量子通信网络中，连续变量量子密钥分发（CVQKD）方案面临着一个挑战，即纠缠源由恶意窃听者控制，尽管它仍然可以产生正的密钥率和安全性，但其性能仍需提高，特别是在秘密密钥率和最大传输距离方面。在本文中，我们提出了一种基于四态离散调制和一种预示性混合线性放大器的方法，以提高CVQKD的性能，其中纠缠源来自恶意窃听者。四态CVQKD通过相空间中的非正交相干态对信息进行编码。它比高斯调制对应方案具有更好的传输距离，特别是在低信噪比（SNR）时。此外，混合线性放大器将一个确定性线性放大器（DLA）和一个无噪声线性放大器（NLA）串联起来，这可以提高放大成功的概率，并减少测量引起的噪声代价。此外，混合线性放大器可以提高CVQKD的SNR，并在高增益模式和高降噪模式这两种性能之间进行调整，因此在纠缠源不可信的情况下，它可以扩展最大传输距离。
