Quantum key distribution (QKD) provides a secure method to exchange encrypted information between two parties in a quantum communication infrastructure (QCI). The primary challenge in deploying a QCI is the cost of using optical fibers and trusted repeater nodes (TRNs). Practical systems combine quantum and classical channels on the same fiber to reduce the cost of fibers dedicated to QKD. In such a system with quantum-classical coexistence, the optimal distribution of QKD requests with minimal deployment cost and power usage on the multiplexed links is challenging due to the diverse key rate demands of the requests, number of classical and quantum channels, guard band spacing between classical and quantum channels, and secret key rate of the quantum channels that decreases with distance. To address these challenges, in this work, we propose a Steiner tree-based approach for constructing a QCI that connects all quantum nodes with minimum TRNs. In addition, we propose a genetic algorithm-based solution to optimally distribute the end-to-end QKD requests over the QCI. We also determine feasible optical bypass routes to reduce the overall energy consumption in the network further. The proposed approach reduces the QCI deployment cost by 19.42% compared to the benchmark MST-Baseline. Also, on average, TAQNet with optical bypass achieves 4.69 kbit per Joule more energy efficiency compared to the nonbypass approach.
Quantum key distribution (QKD) provides a secure method to exchange encrypted information between two parties in a quantum communication infrastructure (QCI). The primary challenge in deploying a QCI is the cost of using optical fibers and trusted repeater nodes (TRNs). Practical systems combine quantum and classical channels on the same fiber to reduce the cost of fibers dedicated to QKD. In such a system with quantum-classical coexistence, the optimal distribution of QKD requests with minimal deployment cost and power usage on the multiplexed links is challenging due to the diverse key rate demands of the requests, number of classical and quantum channels, guard band spacing between classical and quantum channels, and secret key rate of the quantum channels that decreases with distance. To address these challenges, in this work, we propose a Steiner tree-based approach for constructing a QCI that connects all quantum nodes with minimum TRNs. In addition, we propose a genetic algorithm-based solution to optimally distribute the end-to-end QKD requests over the QCI. We also determine feasible optical bypass routes to reduce the overall energy consumption in the network further. The proposed approach reduces the QCI deployment cost by 19.42% compared to the benchmark MST-Baseline. Also, on average, TAQNet with optical bypass achieves 4.69 kbit per Joule more energy efficiency compared to the nonbypass approach.
Quantum communication infrastructure (QCI) is gradually becoming a favorable choice for transmitting secure data across the globe. Network operators often prefer to utilize the existing network infrastructure to reduce network setup costs to build a QCI. This implies transforming traditional network nodes to quantum nodes (QNs) by equipping them with quantum processors. Trusted repeater nodes (TRNs) are used to connect distant QNs. However, the network infrastructure cost increases with the number of TRNs due to the usage of dark fibers. Therefore, it is challenging for the network planning to build a QCI that connects all QNs with a minimum number of TRNs to reduce the infrastructure cost. In this work, we construct a minimum cost spanning tree for the QCI to connect all QNs with a minimum number of links and TRNs. The proposed approach considers node distance and attenuation cost of the physical connections. Compared to the traditional spanning tree approach, our proposed approach reduces the cost of QCI deployment by 10.90%.
This article proposes an optimization model for the design of quantum communication infrastructures (QCI) with the aim of minimizing capital expenditure (CAPEX), focusing on the costs associated with the deployment of quantum links and trusted repeater nodes. The model is formulated using an integer linear programming (ILP) program that incorporates physical and operational constraints to ensure efficient resource allocation. The simulation results obtained using an ILP solver show that increasing wavelength availability leads to significant reductions in CAPEX while consistently producing solutions that satisfy all constraints. However, because ILP becomes computationally expensive for large-scale networks, we propose two genetic algorithms ( GA1 and GA2 ) designed to improve scalability. Both GA1 and GA2 offer competitive computation times compared with the ILP solver and provide near-optimal solutions compared with the ILP solution. Overall, this approach is effective for small, medium, and large-scale QCI deployments, offering a scalable and practical solution suitable for real-world implementation. For example, in the small network topology with nine nodes and nine requests, we observe a reduction of CAPEX up to 33% when the number of available wavelengths increases from 1 to 2, and we note that GAs in a large topology, such as NET-4 network, reduce CAPEX by 34.6% ( GA1 ), and 21.1% ( GA2 ) compared to the benchmarks.
Quantum key distribution (QKD) uses the laws of quantum mechanics to distribute secret keys with information-theoretic security. To realize QKD for secure communications among multiple distant users, fiber-based QKD networks can be deployed with today's available technologies. Incorporating QKD into existing wavelength-division multiplexing (WDM) network infrastructure provides a practical way to reduce the difficulty and cost of QKD networking. Nonetheless, the costs of QKD nodes and QKD links are still considered as the major barriers to long-distance QKD network deployment in practice. In this work, we study how to minimize the cost of deploying QKD-over-WDM backbone networks. We introduce a general architecture of QKD-over-WDM backbone networks. A novel cost-oriented model is defined to elaborate the cost-minimized problem, in which various QKD network components including QKD transceivers, QKD auxiliary equipment for QKD backbone nodes and trusted repeater nodes (TRNs), and QKD links are considered. The physical-layer parameters such as secret-key rate, physical distance, and the layout of TRNs are also incorporated in our defined model. We develop an integer linear programming (ILP) model and a novel cost-efficient QKD networking (CEQN) heuristic algorithm to address the cost-minimized problem. The extensive simulations indicate that our proposed approaches are effective in reducing the cost of deploying QKD-over-WDM backbone networks, where the designed CEQN algorithm is efficient to demonstrate similar to the ILP model. Finally, some open issues in future work are discussed, given that this work only presents an early highlevel analysis as opposed to a definitive detailed model.
The technological maturity of Quantum Key Distribution (QKD) products have generated high demand for secure key distribution in transmitting sensitive data. To provide this service, long-haul network operators are exploring strategies for network-wide deployment of QKD devices while utilizing existing infrastructure. One approach is to place trusted nodes at existing in-line amplifier huts in the network. In this study, we present a near-optimal fiber span aggregation algorithm, which effectively minimizes the number of trusted nodes between Points-of-Presences (PoPs) in the network. In this study, we evaluate six different topological QKD network deployments and eight different technological QKD network deployments in terms of the total secure key rate, as well as the number of QKD fiber pairs deployed. Our results indicate that the span aggregation algorithm increases the distance between each trusted node by up to 20%, thereby reducing the overall number of trusted nodes. Capacity planning for various topologies and technology deployments on simulated Secure Application Entity (SAE) requests is undertaken. Our proposed capacity planning shows that a baseline deployment with span aggregation using a QKD device with a cut-off distance of 140 km can save up to 3 times the number of QKD deployed fibers as compared to a minimum spanning tree-based low-cost deployment.
Quantum key distribution (QKD) revolutionizes secure communication, offering unbreakable cryptography against quantum computers’ rising computational power. This paper explores the placement of trusted nodes to enhance the efficiency of quantum communication networks. Two practical scenarios are investigated: the multi-band (MB) setting, utilizing different wavelength bands for QKD and classical systems, and the multifiber (MF) solution, employing separate fibers for QKD and classical communication. The study optimizes secret key rate (SKR) per quantum transmitter and receiver (Q-TRx) in metro quantum-optical networks. A heuristic algorithm, considering noise sources and fiber attenuation, is proposed for routing, modulation, spectrum, and time assignment. The simulations conducted on various network topologies reveal optimal QKD trusted node distances (QTND) and wavelengths place. The simulation results indicate that the optimal QTND value for the MB-scenario and MF-scenario is 20 and 25 km, respectively. Compared to scenarios without QKD trusted node placement along the 40 km link, both the MB-scenario and MF-scenario exhibit 40% and 15% improvements, respectively, in SKR/QTRx relative to their optimal QTND values.
Quantum communication ensures that data remains secure from unauthorized access. Despite these advantages, this technology faces several challenges. For instance, photons can be lost when they go through channels, and there is a chance of eavesdropping, that make the system not as trustworthy, safe, and efficient. To make quantum communication systems function effectively in the real world, we need to combine advanced technologies like quantum error correction mechanisms and quantum repeaters. This work suggests a unified Quantum Inspired Genetic Algorithm (QIGA) framework that utilizes collaborative quantum repeaters to conquer the limitations of network links over distance. This study introduces a hybrid optimization topology (OT) that integrates mesh, star, and ring configurations for measurement device-independent quantum key distribution (MDI-QKD) networks. This approach allows for the efficient use of resources for scalable quantum communication networks. The proposed network architecture integrates 12 user nodes, a trusted node, and a single shared quantum repeater within a hybrid topology. The repeater deployment has been designed to support links that are longer than 52 km. This design accommodates deployments on various scales, small, medium, and large, while optimizing resource usage and infrastructure costs. We evaluated the performance and security trade offs in quantum communication networks by optimizing three topologies with a QIGA: ring, ring-star, and ring-star-mesh hybrid (QIGA−OT). The optimization methodology aims to reconcile essential performance metrics, such as the Secure Key Rate (SKR), Quantum Bit Error Rate (QBER), channel loss, and Merit of Quantum Efficiency (MQE). MQE functions as a metric for evaluating trades concerning security, efficiency, and cost-effectiveness within the network. This work presents a novel approach for utilizing quantum-inspired in the effective design and implementation of scalable network topologies across numerous fields of application.