The quantum internet promises unparalleled capabilities that are provably impossible with the classical internet. However, current quantum networks are often designed with dedicated systems for specified tasks, which hinders the openness and diversity of future quantum internet. To address these limitations, this work proposes a fully heterogeneous quantum network accompanied with several techniques. Our proposal allows users to access the network using any mainstream systems or even partial systems. The network also enables the execution of multiple distinct quantum tasks and provides opportunities for global optimization and cost-efficient design. A five-node quantum network featuring heterogeneous nodes has been implemented, demonstrating the superiority of our proposal through tasks such as quantum key distribution, quantum digital signature, quantum Byzantine agreement, and quantum conference. Notably, the experiment represents the first demonstration of multi-malicious node quantum Byzantine agreement in a quantum network. This work proposed a fully heterogeneous quantum network that connects diverse user systems and enables multiple quantum tasks. A software-defined quantum network structure is also proposed for coordinating network nodes and optimizing network performance. It paves the way for an open and versatile quantum internet.
The quantum internet promises unparalleled capabilities that are provably impossible with the classical internet. However, current quantum networks are often designed with dedicated systems for specified tasks, which hinders the openness and diversity of future quantum internet. To address these limitations, this work proposes a fully heterogeneous quantum network accompanied with several techniques. Our proposal allows users to access the network using any mainstream systems or even partial systems. The network also enables the execution of multiple distinct quantum tasks and provides opportunities for global optimization and cost-efficient design. A five-node quantum network featuring heterogeneous nodes has been implemented, demonstrating the superiority of our proposal through tasks such as quantum key distribution, quantum digital signature, quantum Byzantine agreement, and quantum conference. Notably, the experiment represents the first demonstration of multi-malicious node quantum Byzantine agreement in a quantum network. This work proposed a fully heterogeneous quantum network that connects diverse user systems and enables multiple quantum tasks. A software-defined quantum network structure is also proposed for coordinating network nodes and optimizing network performance. It paves the way for an open and versatile quantum internet.
The quantum internet is envisaged to connect quantum systems at a global scale to provide diverse applications unimaginable with the classical internet. However, the technological shortcomings and practical challenges of noisy intermediate-scale quantum (NISQ) devices impose several constraints on the vision of a truly global quantum internet. Recent experimental developments for quantum networks are laying the pathway from small-scale to intermediate-scale noisy quantum networks dedicated to specific operational tasks. Although these networks are not at the global scale, they are capable of providing a clear quantum advantage in their dedicated tasks. We explore the cardinal features of these NISQ networks, discuss their design constraints, and explore the possible applications they provide. We also outline some technical challenges that need to be addressed for the practical implementation of these networks and eventually lead toward a truly global, fully functional quantum internet.
Quantum networks are needed for quantum domain applications that may run across different network deployments - point-to-point, multi-node networks, and possibly across inter-domain quantum networks, like the quantum internet. Unlike classical computing networks, quantum networks involve heterogeneous systems nodes that currently require local and manual control. This needs a unified control approach to help them integrate, work seamlessly, and have global knowledge. Software-defined Networking (SDN) has been successfully leveraged in classical networking for seamless and software-driven control of network infrastructure and packet switching, but not in management of quantum network applications across heterogeneous systems. In this paper, we review the current state of the art and present early developments of a System-of-Systems Software-defined Quantum Networking architecture (SoS-SDQN), a generic architecture that supports software-driven quantum network experiments across heterogeneous quantum systems. The architecture modifies the generic SDN to address the domain requirements of quantum networks and proposes a multilevel SDQN to provide a global view of network status, running applications, and control of incorporated heterogeneous quantum systems. We also design and implement a SoS SouthBound Quantum Interface (SoS-SBQI), a quantum infrastructure protocol that abstracts automation of applications across the network.
Quantum network is a research topic involving fundamental quantum information science, engineering designs, and experimental implementations. Existing research works primarily pertain to theoretical architecture designs and proof-of-concept experimental demonstrations. With the recent developments in engineering quantum systems, the realization of scalable local-area quantum networks has become viable. However, the design and implementation of a quantum network is a holistic task that is way beyond the scope of an abstract design problem. As such, a testbed on which multiple disciplines can verify the design and implementation across a full networking stack has become a necessary infrastructure for the future development of quantum networks. In this work, we demonstrate the concept of quantum internet service provider (QISP), in analogy to the conventional ISP that allows for the sharing of classical information between the network nodes. The QISP is significant for the next-generation quantum networks as it coordinates the production, management, control, and sharing of quantum information across the end-users of a quantum network. We construct a reconfigurable QISP comprising both the quantum hardware and classical control software. Building on the fiber-based quantum-network testbed of the Center for Quantum Networks (CQN) at the University of Arizona (UA), we develop an integrated QISP prototype based on a Platform-as-a-Service (PaaS) architecture, whose classical control software is abstracted and modularized as an open-source QISP framework. To verify and characterize the QISP's performance, we demonstrate multi-channel entanglement distribution and routing among multiple quantum-network nodes with a time-energy entangled-photon source. We further perform field tests of concurrent services for multiple users across the quantum-network testbed. Our experiment demonstrates the robust capabilities of the QISP, laying the foundation for the design and verification of architectures and protocols for future quantum networks.
In the initial stage of the quantum Internet, most of the practical quantum networks have been deployed relying on diverse individual quantum key distribution (QKD) protocols. However, this single-protocol paradigm cannot fulfill the heterogeneous requirements of the users, hence market-penetration of quantum networks is limited. Given the recent advances in QKD protocols, the next generation quantum networks are expected to support both legacy and emerging QKD protocols. However, the evolution from single-protocol to multi-protocol quantum networks poses numerous challenging problems. As a remedy, we conceive a practical protocol translation framework for supporting this migration from single-protocol to large-scale multi-protocol quantum networks. Furthermore, we propose a programmable multi-functional relay node architecture for harmonizing the components of a suitable relay node. A pair of protocol translation policies are presented for meeting the challenging security requirements of migration requests, which are compared to the single-protocol-based migration solutions both in terms of the translation success probability attained (i.e., the proportion of migration requests with successful protocol translation), and the average relaying risk probability encountered (i.e., the mean of the relaying risk probabilities of end-to-end key negotiation in a quantum network). Finally, we highlight a suite of open problems in both quantum secure direct communication and quantum teleportation for research into future multi-protocol quantum networks.
Quantum key distribution (QKD) is an essential branch of quantum communications that facilitates future-proof security. In the near future, large-scale quantum networks will inevitably encounter diverse QKD protocols, ultimately resulting in a multi-protocol quantum network. Motivated by the evolution of advanced QKD protocols, this article introduces a pivotal enabler for multi-protocol quantum networks: software-defined heterogeneous QKD chaining (HQKDC). In contrast to the conventional QKD chain using a single protocol and a single connectivity pattern, a heterogeneous QKD chain is established relying on multiple protocols and diverse connectivity patterns. We elaborate the HQKDC framework by describing the structures of various QKD chains and proposing an architecture of software-defined HQKDC over optical networks. The software defined networking paradigm and optical networks can facilitate the orchestration and deployment of heterogeneous QKD chains, respectively. Furthermore, we present and evaluate the strategies for heterogeneous QKD chain deployment, as well as devise and demonstrate the workflow for heterogeneous QKD chain orchestration. Finally, we discuss open issues toward the practical QKD network and quantum Internet.
As quantum networking hardware remains costly and not yet widely accessible, simulation tools are essential for the design and evaluation of quantum network architectures and protocols. However, designing a scalable and computationally efficient quantum network simulator is intrinsically challenging: i) quantum dynamics must be emulated on classical computing platforms while capturing the stateful and non-local nature of entanglement, a quantum resource without any classical networking analog; ii) quantum networking is inherently hybrid, as protocol execution also fundamentally depends on classical signaling. This makes a tight and faithful co-simulation of quantum operations and classical message exchanges a core requirement. In this light, we present Q2NS, a modular and extensible quantum network simulator, built on top of ns-3, designed to seamlessly integrate quantum-network primitives with ns-3's established classical protocol stack. Q2NS adopts a modular architecture that decouples protocol control logic from node- and channel-level operations, enabling rapid prototyping and adaptation across heterogeneous and evolving Quantum Internet scenarios. Q2NS natively supports multiple quantum state representations through a unified interface, allowing interchangeable state-vector, density-matrix, and stabilizer backends. We validate Q2NS through realistic use-case studies and comprehensive benchmarks, demonstrating superior computational efficiency over representative state-of-the-art alternatives, while preserving modeling flexibility. Finally, we provide a dedicated visualization tool that jointly captures physical and entanglement-enabled connectivity and supports entangled-state manipulations, facilitating an intuitive interpretation of entanglement dynamics and protocol behavior. Q2NS offers a flexible, open, and scalable simulation platform for advancing Quantum Internet research.