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arXiv:2104.04155 · Optics Express

Optimizing the deployment of quantum key distribution switch-based networks

A. Tayduganov, V.E. Rodimin, Evgeniy O. Kiktenko, V. L. Kurochkin, Evgeniy Krivoshein, Sergey Khanenkov, Vasilisa Usova, Lyudmila Stefanenko, Yury Kurochkin, Aleksey K. Fedorov

Published Jun 22, 2021• 14 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) networks provide an infrastructure for establishing information-theoretic secure keys between legitimate parties via quantum and authentic classical channels. The deployment of QKD networks in real-world conditions faces several challenges, which are related in particular to the high costs of QKD devices and the condition to provide reasonable secret key rates. In this work, we present a QKD network architecture that provides a significant reduction in the cost of deploying QKD networks by using optical switches and reducing the number of QKD receiver devices, which use single-photon detectors. We describe the corresponding modification of the QKD network protocol. We also provide estimations for a network link of a total of 670 km length consisting of 8 nodes and demonstrate that the switch-based architecture achieves significant resource savings of up to 28%, while the throughput is reduced by 8% only.

DOI
10.1364/oe.427804

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Quantum key distribution (QKD) networks provide an infrastructure for establishing information-theoretic secure keys between legitimate parties via quantum and authentic classical channels. The deployment of QKD networks in real-world conditions faces several challenges, which are related in particular to the high costs of QKD devices and the condition to provide reasonable secret key rates. In this work, we present a QKD network architecture that provides a significant reduction in the cost of deploying QKD networks by using optical switches and reducing the number of QKD receiver devices, which use single-photon detectors. We describe the corresponding modification of the QKD network protocol. We also provide estimations for a network link of a total of 670 km length consisting of 8 nodes and demonstrate that the switch-based architecture achieves significant resource savings of up to 28%, while the throughput is reduced by 8% only.
Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.
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As the limitations of classical cryptographic systems become increasingly evident in the face of advancing quantum algorithms, Quantum Key Distribution (QKD) emerges as a vital paradigm for securing information in next-generation networks. This paper explores the theoretical foundations and protocol architectures underpinning QKD, including BB84, E91, and newer hybrid approaches designed for scalable integration into existing infrastructures. Performance metrics such as key generation rate, error thresholds, and resistance to various attack models are critically examined across both fiber-optic and free-space implementations. Furthermore, the study delves into real-world deployment challenges—ranging from synchronization errors and quantum channel noise to cost-efficiency and interoperability with classical systems. By offering a comparative analysis and proposing optimization strategies, this work aims to pave the way for robust quantum-secure communication protocols suited for large-scale, heterogeneous network environments.
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The advent of cryptographically relevant quantum computers poses an existential threat to classical public-key infrastructure. Quantum Key Distribution (QKD) addresses this challenge by providing information-theoretic security for key establishment, independently of any computational hardness assumption. In this work, the deployment and experimental validation of a metropolitan-scale quantum-secure network between data centers in Milan is reported. The network operates over installed fiber infrastructure and implements a layered architecture integrating QKD hardware, standards-compliant Key Management (KM), and centralized Software-Defined Networking (SDN) orchestration. Dynamic path reconfiguration via active optical switching and trusted-node routing allow automated fail-over solutions. Application-layer validation across diverse protocols and workloads confirms the seamless interoperability of all system components. These results establish the technical and operational readiness of metropolitan QKD networks for production deployment, and offer a replicable blueprint for building quantum-secure communication infrastructure at metropolitan scale.
Current technological progress is driving Quantum Key Distribution towards a commercial and worldwide scale expansion. Its capability to deliver secure communication regardless of the computational power of the attackers will be a fundamental feature in the next generations of telecommunication networks. Nevertheless, demonstrations of QKD implementation in a real operating scenario and their coexistence with the classical telecom infrastructure are of fundamental importance for reliable exploitation. Here we present a Quantum Key Distribution application implemented over a classical fiber-based infrastructure. We exploit a 50 MHz source at 1550 nm, a single 13 km-long fiber cable for both the quantum and the classical channel, and a simplified receiver scheme with just one single-photon detector. In this way, we achieve an error rate of approximately 2% and a secret key rate of about 1.7 kbps, thus demonstrating the feasibility of low-cost and ready-to-use Quantum Key Distribution systems compatible with standard classical infrastructure.