QKD in existing networks

Mariani, Luca, Raja Yehia, Carlos Pascual-García +4 more

There exist several initiatives worldwide to deploy quantum key distribution (QKD) over existing fibre networks and achieve quantum-safe security at large scales. To understand the overall QKD network performance, it is required to transition from the analysis of individual links, as done so far, to the characterization of the network as a whole. In this work, we undertake this study by embedding QKD protocols on complex networks, which correctly model the existing fiber networks. We focus on networks with trusted nodes and on continuous-variable (CV) schemes, which have much higher key rates than their discrete-variable (DV) counterparts. In the effective CV network, however, many of the unique properties of complex networks, such as small-worldness and the presence of hubs, are lost due to the fast decay of the key rate with physical distance for CV systems. These properties can be restored when considering a hybrid network consisting of both CV and DV protocols, achieving at the same time high average rate and inter-connectivity. Our work opens the path to the study of QKD complex networks in existing infrastructures.

Oliver Maurhart

Anne de Chastenet, Eric Augé, Gonzague Reydet +3 more

Wanrong Yu, Baokang Zhao, Zhe Yan

Based on the analysis of quantum key distribution (QKD) scenarios, existing point-to-point QKD systems need to be networked for satisfied actual applications. However, the architecture and network layer protocols of existing QKD network have lots of limitations, such as excessive key consumption and inability to achieve random routing. In this paper, we propose the software defined quantum key distribution network (SQN). We introduce the design of the architecture and critical modules for SQN. Analysis results show that SQN can efficiently reduce the secure key consumption and improve the availability and performance of QKD network.

M. Suda

Xingxiang Peng, Pin Lü, Yong Ying +15 more

The co-existence of quantum key distribution (QKD) signals with classical optical signals in a single fiber enables substantial fiber resource savings and reduces the deployment costs of QKD networks. However, conventional approaches to mitigate the impact of strong classical signals on QKD performance typically involve reducing classical optical power, which inherently conflicts with standard optical communication network specifications and impedes the widespread adoption of QKD networks. In this work, we explore the feasibility of integrating QKD networks with high-capacity classical optical networks without significant modifications to existing infrastructure and validate wavelength allocation strategies for their co-existence in field-deployed shared fibers. Notably, we demonstrate co- propagation of QKD with high-power classical signals (21.75 dBm total launch power) over 81 km of commercial backbone fiber, covering 90% of China Telecom's inter-site links. Leveraging a 400 Gbps optical transport network (OTN) system, we first, to the best of our knowledge, achieve a classical optical capacity of 15.7 Tbps. Additionally, we introduce single-fiber optical supervisory channel (OSC) configurations in quantum-classical co-existence experiments for the first time, further validating the feasibility of integrating QKD networks with classical networks requiring high-precision clock synchronization. The system achieves secure key rates (SKRs) of 2.2 kbps and 1.35 kbps under two-fiber and single-fiber OSC configurations, respectively. This study marks a significant step towards the practical deployment and maturity of QKD networks.