Spatial-mode diversity and multiplexing for continuous variables quantum communications

Quantum communication is a key enabler of future secure networks, but its performance is often limited by noise, channel fading, and interference. Current systems struggle to maintain high fidelity and key rates under realistic, dynamic channel conditions. Here, we show that continuous-variable quantum communication systems can benefit significantly from spatial-mode diversity combined with tailored amplification strategies, depending on the available knowledge of the channel. We model the effects of fading as a log-normal distribution and evaluate different amplification approaches at the transmitter and receiver. Our results demonstrate improved fidelity and robustness against noise and fading, especially in harsh environments. We also find that, in certain conditions, spatial-mode diversity provides higher secret key rates than conventional multiplexing strategies in continuous-variable quantum key distribution. These findings highlight the potential of diversity techniques to enhance the stability and scalability of quantum communication networks in practical deployments.