We propose a frequency-division multiplexed (FDM) continuous-variable quantum key distribution (CV-QKD) system with enhanced spectral efficiency through optimized channel spacing of low-symbol-rate signals. A four-channel 10-Mbaud FDM-CV-QKD system was experimentally demonstrated using Gaussian modulation, a transmitted local oscillator, and homodyne detection. Despite the inter-channel interference, under a finite-size scenario (m=1.25x10^6), the system achieved a 3.6-fold back-to-back secret key rate gain and outperformed the single-channel frequency-upconverted signal up to 26.8 km.

翻译：我们提出了一种频分复用（FDM）连续变量量子密钥分发（CV-QKD）系统，通过优化低符号速率信号的通道间隔，实现了频谱效率的提升。实验上展示了使用高斯调制、传输本地振荡器及零差检测的四通道10-Mbaud FDM-CV-QKD系统。尽管存在通道间干扰，在有限尺寸场景（m=1.25×10^6）下，该系统实现了3.6倍的背对背密钥率增益，并在长达26.8 km的距离上优于单通道频率上变频信号。