Making Quantum Networks Work: Routing, Calibration, and Programmable Quantum Repeaters

A thesis on architecture, routing, and operation of quantum repeater networks under realistic constraints

Vinay Kumar· 2026· DOI 10.48550/arXiv.2606.22316

The core problem

The quantum internet promises distribution of quantum states across distant nodes, enabling secure communication, distributed computing, and quantum sensing. However, unlike classical networks, it is constrained by the no-cloning theorem, probabilistic entanglement generation, decoherence, and hardware drift. These constraints render classical network abstractions inadequate. Scalable quantum networking therefore requires new architectures, protocols, and optimisation methods that explicitly account for these limitations. This thesis studies the architecture, routing, and operation of quantum networks under realistic constraints, focusing on bipartite entanglement distribution over quantum repeater networks. Key performance metrics include end-to-end fidelity, throughput, scalability, and fairness. The work spans network-layer routing, link-layer calibration, and a hardware-software interface via an instruction set architecture for programmable quantum repeater nodes.

The proposed routing strategies demonstrate improved fidelity and reduced path blocking under heterogeneous repeater efficiencies. Grey-box routing achieves robustness and fairness without requiring detailed link information, relying solely on topology and end-to-end estimates. For linear repeater chains, the optimal calibration schedule balances operation time and calibration overhead, leading to efficient resource utilisation. The greedy orchestration heuristic for general topologies with shared links provides a scalable solution for calibration scheduling. The instruction set architecture for programmable quantum repeater nodes based on NV centers enables coherent programmability, linking physical operations to higher-layer protocols. Quantitative results include improvements in end-to-end fidelity, throughput, and fairness metrics, although specific numerical values are not provided in the abstract. The thesis demonstrates that accounting for realistic constraints such as probabilistic entanglement generation, decoherence, and hardware drift is essential for scalable quantum networking.

The quantum internet promises distribution of quantum states across distant nodes, enabling secure communication, distributed computing, and quantum sensing. However, unlike classical networks, it is constrained by the no-cloning theorem, probabilistic entanglement generation, decoherence, and hardware drift. These constraints render classical network abstractions inadequate. Scalable quantum networking therefore requires new architectures, protocols, and optimisation methods that explicitly account for these limitations. This thesis studies the architecture, routing, and operation of quantum networks under realistic constraints, focusing on bipartite entanglement distribution over quantum repeater networks. Key performance metrics include end-to-end fidelity, throughput, scalability, and fairness. The work spans network-layer routing, link-layer calibration, and a hardware-software interface via an instruction set architecture for programmable quantum repeater nodes.

The thesis employs a combination of analytical modelling, simulation, and architectural design. At the network layer, routing strategies are developed beyond assumptions of homogeneous nodes and full network knowledge. Routing under heterogeneous repeater efficiencies is analysed to show how partial knowledge of node quality improves fidelity and reduces path blocking. A grey-box routing approach is introduced, where path selection relies only on topology and end-to-end estimates, achieving robustness and fairness without detailed link information. At the link layer, calibration and hardware drift are addressed through a calibration-aware model that separates activation and calibration phases. For linear repeater chains, an optimal calibration schedule is derived to balance operation time and calibration overhead. This is extended to general topologies with shared links, where a greedy orchestration heuristic is proposed. Finally, the thesis connects network protocols with hardware via an instruction set architecture for programmable quantum repeater nodes based on NV centers, enabling coherent programmability and linking physical operations to higher-layer protocols. The methodology includes mathematical derivations, algorithmic design, and simulation-based evaluation.

The thesis highlights the inadequacy of classical network abstractions for quantum networks due to fundamental differences such as the no-cloning theorem and probabilistic entanglement generation. The proposed routing strategies address the challenge of heterogeneous nodes and partial network knowledge, showing that grey-box approaches can achieve robustness and fairness. The calibration-aware model and optimal schedules mitigate the effects of hardware drift, which is a critical practical issue. The instruction set architecture bridges the gap between hardware and software, enabling programmability and integration with higher-layer protocols. The work contributes to the development of scalable quantum networks by providing architectures, protocols, and optimisation methods that explicitly account for realistic constraints. Future directions may include extending the approaches to multi-partite entanglement and more complex topologies, as well as experimental validation on physical quantum repeater platforms.

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