Quantum entanglement generation and distribution is key to the vision for a Quantum Internet. Existing research has focused on entanglement routing schemes and QR performance in a general network setting with strong physical layer assumptions. In reality, the required quantum memory and quantum repeater devices along with the control protocols for general quantum networks remain grand challenges in the foreseeable future. Main performance concerns at the networking layer include entanglement distribution rate and fidelity. We thereafter propose to focus more research efforts on the quantum data center network due to its structured topology and potential to support emerging distributed quantum computing applications. This paper presents a quantum data center (QDC) network architecture with novel switch architecture and protocols that feature locally buffered entanglement qubits and centralized on-demand entanglement generation and distribution. Queueing models for the switches and large-scale network simulation with the NetSquid quantum simulator demonstrate the high network throughput, scalability, and fidelity performance for the proposed QDC network architecture and protocol.
Quantum entanglement generation and distribution is key to the vision for a Quantum Internet. Existing research has focused on entanglement routing schemes and QR performance in a general network setting with strong physical layer assumptions. In reality, the required quantum memory and quantum repeater devices along with the control protocols for general quantum networks remain grand challenges in the foreseeable future. Main performance concerns at the networking layer include entanglement distribution rate and fidelity. We thereafter propose to focus more research efforts on the quantum data center network due to its structured topology and potential to support emerging distributed quantum computing applications. This paper presents a quantum data center (QDC) network architecture with novel switch architecture and protocols that feature locally buffered entanglement qubits and centralized on-demand entanglement generation and distribution. Queueing models for the switches and large-scale network simulation with the NetSquid quantum simulator demonstrate the high network throughput, scalability, and fidelity performance for the proposed QDC network architecture and protocol.
Quantum Data Centers (QDCs) are needed to support large-scale quantum processing for both academic and commercial applications. While large-scale quantum computers are constrained by technological and financial barriers, a modular approach that clusters small quantum computers offers an alternative. This approach, however, introduces new challenges in network scalability, entanglement generation, and quantum memory management. In this paper, we propose a three-layer fat-tree network architecture for QDCs, designed to address these challenges. Our architecture features a unique leaf switch and an advanced swapping spine switch design, optimized to handle high volumes of entanglement requests as well as a queue scheduling mechanism that efficiently manages quantum memory to prevent decoherence. Through queuing-theoretical models and simulations in NetSquid, we demonstrate the proposed architecture's scalability and effectiveness in maintaining high entanglement fidelity, offering a practical path forward for modular QDC networks.
The emergence of quantum networks promises revolutionary advancements in secure communication, computational power, and information processing. This paper provides insights into the essential components and architecture of quantum networks. We systematically examine each layer of the quantum protocol stack, from the physical layer responsible for qubit transmission and entanglement generation to the transport layer ensuring reliable qubit communication, up to the application layer enabling quantum key distribution and quantum computing applications. In this work, we introduce the E-QNet framework, an entanglement-assisted quantum network protocol stack designed to facilitate quantum communication. Key devices such as quantum transceivers, entanglement sources, quantum memories, quantum repeaters, and quantum routers are analyzed in the context of their specific roles and functionalities. We draw parallels with classical network architecture, highlighting both the unique challenges and novel solutions inherent in quantum networking. By elucidating the interplay between hardware devices and protocol layers, this article provides a comprehensive overview of the current state and future directions in quantum network design, offering valuable insights for researchers and engineers in the field. This work aims to contribute to the foundational understanding required for the development and implementation of robust quantum networks.
Entanglement-based networks (EBNs) enable general-purpose quantum communication by combining entanglement and its swapping in a sequence that addresses the challenges of achieving long-distance communication with high fidelity associated with quantum technologies. In this context, entanglement distribution refers to the process by which two nodes in a quantum network share an entangled state, serving as a fundamental resource for communication. In this paper, we study the performance of entanglement distribution mechanisms over a physical topology comprising end nodes and quantum switches, which are crucial for constructing large-scale links. To this end, we implemented a switch-based topology in NetSquid and conducted a series of simulation experiments to gain insight into practical and realistic quantum network engineering challenges. These challenges include, on the one hand, aspects related to quantum technology, such as memory technology, gate durations, and noise; and, on the other hand, factors associated with the distribution process, such as the number of switches, distances, purification, and error correction. All these factors significantly impact the end-to-end fidelity across a path, which supports communication between two quantum nodes. We use these experiments to derive some guidelines towards the design and configuration of future EBNs.
Large-scale quantum networks with thousands of nodes require scalable network protocols and physical hardware to realize. In this work, we introduce packet switching as a new paradigm for quantum data transmission in both future and near-term quantum networks. We propose a classical-quantum data frame structure and explore methods of frame generation and processing. Further, we present conceptual designs for a quantum reconfigurable optical add-drop multiplexer to realize the proposed transmission scheme. Packet switching allows for a universal design for a next generation Internet where classical and quantum data share the same network protocols and infrastructure. In this new quantum networking paradigm, entanglement distribution, as with quantum key distribution, is an application built on top of the quantum network rather than as a network designed especially for those purposes. For analysis of the network model, we simulate the feasibility of quantum packet switching for some preliminary models of quantum key and entanglement distribution. Finally, we discuss how our model can be integrated with other network models toward a realization of a quantum Internet.
Quantum data-center (QDC) architectures aim to scale distributed quantum computing (DQC) by interconnecting multiple quantum processing units (QPUs), but their performance depends strongly on how algorithmic communication patterns interact with entanglement generation, switch reconfiguration, and network topology. This paper studies the Quantum Approximate Optimization Algorithm (QAOA) as a graph-structured optimization workload for QDC-based distributed quantum computing. We adapt QAOA to SwitchQNet, a distributed quantum compiler framework that schedules communication and entanglement generation over switch-based QDC networks, by adding a routing generator that converts graph-dependent two-qubit cost interactions into remote-CX communication requests across QPUs. Using this extension, we evaluate QAOA instances across Clos, fat-tree, and spine-leaf topologies, measuring communication latency, EPR-pair overhead, EPR wait time, retry overhead, and sensitivity to buffer size, look-ahead depth, communication-qubit count, EPR latency, and EPR fidelity assumptions. The results show that QAOA obtains modest but consistent latency reductions, highlighting its value as a diagnostic benchmark for studying the interaction between algorithm structure, entanglement management, and quantum-network architecture.
The Quantum Internet is key for distributed quantum computing, by interconnecting multiple quantum processors into a virtual quantum computation system. This allows for scaling the number of qubits by overcoming the inherent limitations of noisy intermediate-scale quantum devices. Thus, the Quantum Internet is the foundation for large-scale, fault-tolerant quantum computation. Among the distributed architectures, quantum data centres emerge as the most viable in the medium term, since they integrate multiple quantum processors within a localized network infrastructure, by allowing modular design of quantum networking. We analyse the physical and topological constraints of quantum data centres, by emphasizing the role of entanglement orchestrators in dynamically reconfiguring network topologies through local operations. We examine the major hardware challenge of quantum transduction, essential for interfacing heterogeneous quantum systems. Furthermore, we explore how interconnecting multiple Quantum Data Centres could enable large-scale quantum networks. We discuss the topological constraints of such a scaling and identify open challenges, including entanglement routing and synchronization. The analysis positions quantum data centres as both a practical implementation platform and strategic framework for the future quantum internet. This article is part of the discussion meeting issue 'Bits, neurons and qubits for sustainable AI'.