The quantum internet enables secure communication, distributed quantum computing, and remote sensing by distributing entanglement among distant nodes [1], [2]. However, establishing end-to-end entanglement across regional networks remains challenging because quantum links experience photon loss, entanglement generation is probabilistic, quantum memories have limited coherence times, and repeater resources are constrained [2], [3]. Conventional shortest-path routing does not jointly account for these quantum-specific limitations. This paper proposes a Fidelity- and Coherence-Aware Dynamic Entanglement Routing (FCADR) framework for regional quantum internet networks. The network is modelled as a graph containing end nodes, quantum repeaters, quantum memories, and lossy entanglement links. FCADR selects routes by jointly considering estimated end-to-end fidelity, entanglement-generation and swapping success probabilities, available quantum-memory capacity, and expected distribution delay. A discrete-event simulation framework is designed to compare FCADR with shortest-path routing, link-success-based routing, and fidelity-aware routing under varying channel loss, coherence time, traffic load, and node or link failures. Performance is evaluated using end-to-end fidelity, request-success rate, distribution delay, memory utilization, and network resilience. The framework aims to improve routing decisions by incorporating quantum-state quality and resource availability into dynamic path selection.
The quantum internet enables secure communication, distributed quantum computing, and remote sensing by distributing entanglement among distant nodes [1], [2]. However, establishing end-to-end entanglement across regional networks remains challenging because quantum links experience photon loss, entanglement generation is probabilistic, quantum memories have limited coherence times, and repeater resources are constrained [2], [3]. Conventional shortest-path routing does not jointly account for these quantum-specific limitations. This paper proposes a Fidelity- and Coherence-Aware Dynamic Entanglement Routing (FCADR) framework for regional quantum internet networks. The network is modelled as a graph containing end nodes, quantum repeaters, quantum memories, and lossy entanglement links. FCADR selects routes by jointly considering estimated end-to-end fidelity, entanglement-generation and swapping success probabilities, available quantum-memory capacity, and expected distribution delay. A discrete-event simulation framework is designed to compare FCADR with shortest-path routing, link-success-based routing, and fidelity-aware routing under varying channel loss, coherence time, traffic load, and node or link failures. Performance is evaluated using end-to-end fidelity, request-success rate, distribution delay, memory utilization, and network resilience. The framework aims to improve routing decisions by incorporating quantum-state quality and resource availability into dynamic path selection.
Distributed quantum computing (DQC) connects multiple quantum processing units (QPUs) via quantum interconnects to overcome the qubit-count and connectivity limitations of individual devices. A critical challenge in this paradigm is routing entanglement resources efficiently across the quantum interconnect network so that inter-QPU quantum gates can be executed with high fidelity and minimal resource waste. We propose the Entanglement-Aware Adaptive Routing (EAAR) framework, which jointly optimizes path selection, entanglement purification scheduling, and congestion-aware load balancing for DQC workloads. EAAR models the quantum network as a fidelity-weighted directed graph and transforms the maximum-fidelity path problem into an additive shortest-path problem. An adaptive purification scheduler targets bottleneck links when end-to-end fidelity falls below application-defined thresholds, and a dynamic congestion penalty steers traffic away from over-utilized entanglement buffers. We evaluate EAAR in simulation across grid, ring, random-regular, and small-world topologies ranging from 4 to 24 QPU nodes. Results demonstrate that EAAR improves average remote-gate fidelity by up to 10.3% and reduces entanglement consumption by up to 44.8% compared to greedy baselines, while maintaining competitive latency with shortest-path routing. These findings confirm that holistic, entanglement-aware routing is essential for practical, high-fidelity distributed quantum computation.
Future quantum networks will enable the interconnection of multiple users distributed across vast geographic distances. Due to these large separations and limited physical resources, communication will often rely on multi-path routing strategies, where physical resources are distributed across channels of varying lengths and delivered to end users. Efficient long-distance quantum communication therefore requires optimizing the allocation of these resources across available paths. In this work, we introduce a performance-oriented approach to quantum network routing by extending the classical concept of Quality of Service (QoS) to the context of multi-path quantum resources distribution. Unlike prior models that consider entanglement generation or quantum memory coherence in isolation, we investigate the interplay between path assignment strategies, coherence time constraints, and quantum error correction (QEC), and how they jointly impact end-to-end communication fidelity. We analyze both unencoded and encoded transmissions over aggregated network paths, quantifying the effects of resource allocation on transmission success. Our findings show that fidelity cannot be optimized independently of memory lifetimes, and that while QEC can enhance performance under specific conditions, it also imposes additional constraints depending on network topology and path-length asymmetries. This work provides a foundation for developing QoS-aware quantum routing protocols that balance fidelity, throughput, and memory utilization -- key considerations for near-term quantum repeater networks.
With the emergence of the Quantum Internet, the need for advanced quantum networking techniques has significantly risen. Various models of quantum repeaters have been presented, each delineating a unique strategy to ensure quantum communication over long distances. We focus on repeaters that employ entanglement generation and swapping. This revolves around establishing remote end-to-end entanglement through repeaters, a concept we denote as the “quantum-native” repeaters (also called “first-generation” repeaters in some literature). The challenges in routing with quantum-native repeaters arise from probabilistic entanglement generation and restricted coherence time. Current approaches use synchronized time slots to search for entanglement-swapping paths, resulting in inefficiencies. Here, we propose a new set of asynchronous routing protocols for quantum networks by incorporating the idea of maintaining a dynamic topology in a distributed manner, which has been extensively studied in classical routing for lossy networks, such as using a destination-oriented directed acyclic graph or a spanning tree. The protocols update the entanglement-link topology asynchronously, identify optimal entanglement-swapping paths, and preserve unused direct-link entanglements. Our results indicate that asynchronous protocols achieve a larger upper bound with an appropriate setting and significantly higher entanglement rate than existing synchronous approaches, and the rate increases with coherence time, suggesting that it will have a much more profound impact on quantum networks as technology advances.
In quantum networks, routing mechanisms designed to deliver successfully multiple simultaneous requests to the destination under limited channel capacity should simultaneously consider resource usage optimization, entanglement-generation performance, and the quality of the end-to-end delivered entangled states. The routing approaches developed for quantum networks in the literature mostly consider the change in fidelity during routing. However, it should be noted that quantum states with the same fidelity value may have different levels of coherence. In this study, for the first time, a novel routing and purification approach for quantum networks is presented, using the end-to-end (E2E) relative entropy of coherence (REC) together with E2E fidelity to determine the purification level and the feasibility of candidate paths. In our study, the coherence- and fidelity-aware routing algorithm (CAFARA) is proposed. In CAFARA, the BBPSSW purification levels are determined for each candidate path and ordered from the lowest to the highest. This information is stored in a lookup table. Then, the lowest BBPSSW purification level that simultaneously satisfies the requested fidelity, REC, latency, and capacity constraints is selected. The E2E fidelity, REC, and required number of raw Bell pairs mentioned here are all stored together in the previously mentioned lookup table. This lookup table was constructed using imperfect initial Werner states, one-sided amplitude damping, Werner-state twirling, BBPSSW purification, and density-matrix-based entanglement swapping, and all calculations were completed before the routing process. As the final step, CAFARA selects the best path with the highest entanglement generation rate (EGR) from the selected feasible paths. In our study, the FARA-PostREC and FARA-NoREC algorithms were developed for comparison with CAFARA. While the FARA-PostREC algorithm uses the REC constraint during the final validation stage of the request, FARA-NoREC does not use any REC constraint; it uses only fidelity as the quality parameter of the paths and as the parameter for determining the purification level. In our simulations under varying link distance, channel capacity, network size, and request load, CAFARA achieved a better average request success rate than FARA-PostREC by reducing late-stage request drops related to coherence because it also uses REC during the purification-level determination stage while maintaining the required E2E fidelity and REC values. Although FARA-NoREC often accepts more requests and assumes that they are successfully delivered, the average final fidelity (AFF) and average final coherence (AFC) values of the requests considered successful are lower than those of the other algorithms; the AFC does not even satisfy the REC threshold. Overall, CAFARA provides a balanced trade-off between the quality-guaranteed request success rate, latency, purification overhead, and resource consumption.
Quantum network can provide end-to-end entanglements through quantum operations, supporting various quantum applications such as quantum key distribution and distributed quantum computing. However, many previous proposals for quantum networks assumed the division of quantum network into time slots and batch processing of network communication tasks, performing poorly in dynamic network scenarios and not fully utilizing network resources. This work focuses on the routing problem in entanglement quantum networks, aiming to provide more efficient end-to-end entanglement establishment for upper-layer applications. We propose an on-demand routing algorithm that dynamically adjusts the optimal path based on the current network conditions. Specifically, we consider the benefits of path width for quantum networks and propose an algorithm for finding the shortest wide path. Using this algorithm, each node establishes its own routing table. Additionally, to dynamically avoid network hotspots, we introduce the concept of traffic to reflect the busyness of nodes. Finally, using a dynamic cost calculation method as the routing metric, we select the optimal path for the current request. To evaluate the performance of the proposed quantum routing algorithm, we conducted simulation experiments on SimQN quantum simulation platform. The results show that our approach improves network throughput by 14 percent compared to existing solutions.
The realization of a large-scale Quantum Internet is a long-term objective of quantum information science, aiming to interconnect quantum devices through the reliable distribution of entanglement across long distances. Unlike classical networks, quantum networks are constrained by decoherence, probabilistic operations, and the no-cloning theorem, which fundamentally alter network design principles. This paper presents a new simulation-driven study of a scalable and resilient Quantum Internet architecture based on adaptive, entanglement-centric networking. A detailed system model is developed, incorporating realistic quantum channel noise, memory decoherence, and repeater-assisted communication. Novel fidelity-aware routing and resource-adaptive entanglement management strategies are evaluated through extensive simulations. Mathematical models, algorithmic pseudocode, and performance analysis demonstrate how adaptive control significantly improves end-to-end fidelity and network throughput under non-ideal conditions. The results provide actionable design insights for future experimental and large-scale quantum networking deployments.