Quantum computing holds great promise and this work proposes to use new quantum data networks (QDNs) to connect multiple small quantum computers to form a cluster. Such a QDN differs from existing quantum key distribution (QKD) networks in that the former must deliver data quantum bits (i.e., qubits) reliably between different quantum computers. Two families of QDNs are studied, one using teleportation, named Tele-QDN, and the other using tell-and-go (TAG), named TAG-QDN. In order to provide reliable delivery of data qubits, while addressing QDN-specific constraints imposed by quantum physics laws such as the no-cloning theorem, and limited availability of quantum memory, two corresponding transport layer protocols suitable for distributed implementation are designed and evaluated. Such distributed quantum transport protocols (DTPs), named Tele-DTP and TAG-DTP, are the first-of-its-kind and are complementary to existing works on the protocol stack for QDNs which are at the network layer and below. Both analysis and extensive simulations show that the proposed DTPs can achieve high throughput and fairness. This study also offers new insights into potential tradeoffs involved in using different types of QDNs.
Quantum computing holds great promise and this work proposes to use new quantum data networks (QDNs) to connect multiple small quantum computers to form a cluster. Such a QDN differs from existing quantum key distribution (QKD) networks in that the former must deliver data quantum bits (i.e., qubits) reliably between different quantum computers. Two families of QDNs are studied, one using teleportation, named Tele-QDN, and the other using tell-and-go (TAG), named TAG-QDN. In order to provide reliable delivery of data qubits, while addressing QDN-specific constraints imposed by quantum physics laws such as the no-cloning theorem, and limited availability of quantum memory, two corresponding transport layer protocols suitable for distributed implementation are designed and evaluated. Such distributed quantum transport protocols (DTPs), named Tele-DTP and TAG-DTP, are the first-of-its-kind and are complementary to existing works on the protocol stack for QDNs which are at the network layer and below. Both analysis and extensive simulations show that the proposed DTPs can achieve high throughput and fairness. This study also offers new insights into potential tradeoffs involved in using different types of QDNs.
Quantum computing holds a great promise and this work proposes to use new quantum data networks (QDNs) to connect multiple small quantum computers to form a cluster. Such a QDN differs from existing QKD networks in that the former must deliver data qubits reliably within itself. Two types of QDNs are studied, one using teleportation and the other using tell-and-go (TAG) to exchange quantum data. Two corresponding quantum transport protocols (QTPs), named Tele-QTP and TAG-QTP, are proposed to address many unique design challenges involved in reliable delivery of data qubits, and constraints imposed by quantum physics laws such as the no-cloning theorem, and limited availability of quantum memory. The proposed Tele-QTP and TAG-QTP are the first transport layer protocols for QDNs, complementing other works on the network protocol stack. Tele-QTP and TAG-QTP have novel mechanisms to support congestion-free and reliable delivery of streams of data qubits by managing the limited quantum memory at end hosts as well as intermediate nodes. Both analysis and extensive simulations show that the proposed QTPs can achieve a high throughput and fairness. This study also offers new insights into potential tradeoffs involved in using the two methods, teleportation and TAG, in two types of QDNs.
Quantum Data Networks (QDNs) are vital to building Distributed Quantum Computing (DQC) systems. Though several communication protocols have been proposed for QDNs, most of them are at the network layer or below. The only transport layer protocol [1] used batch processing of requests for End-to-End (E2E) quantum data transmission. It not only limits the quantum resource utilization, more importantly, it cannot guarantee reliable E2E quantum data transmission. In this paper, we propose the first asynchronous transportation layer protocol, called AQTP, for QDNs to achieve high-speed and reliable E2E quantum data transmission. AQTP has several distinct features: (i) each quantum node locally allocates quantum resources in order to improve scalability; (ii) requests are processed in an asynchronous manner, which results in a higher quantum resource utilization; and (iii) it ensures reliable data transmission even if the teleportation operations fail. Extensive simulations show that compared with a batch processed transport layer protocol, AQTP can increase the network throughput by up to 82.97%, and reduce the Average Task Completion Time (ATCT) of DQC tasks by up to 94.69%.
Quantum Data Networking can significantly transform the landscape of quantum computing by enabling several small quantum computers (QCs) to form a distributed system to achieve the same computing power as a large quantum computer which is infeasible to build. However, this requires quantum state information, in the form of qubits, to be exchanged among multiple geographically distributed QCs, and there are many challenges associated with reliably transferring qubits from one QC to another efficiently. In this paper, we discuss various QDN design options, present main challenges and describe promising solutions to tackle the challenges.
Quantum Data Networks (QDNs) typically leverage teleportation to reliably send data quantum bits (called qubits) to their destinations. To teleport a data qubit from Alice to Bob, one entanglement connection between Alice and Bob needs to be established. Accordingly, we have to establish as many entanglement connections as possible with limited quantum resources in order to maximize the network throughput. Conventional methods assume a known traffic matrix and calculate the paths to establish entanglement connections in one batch using a centralized algorithm. However, these methods are not scalable in large scale QDNs since it is time consuming to optimize the entanglement paths for a batch of requests, which may result in a long time slot duration and significantly reduce the network throughput. To address this issue, we propose an Online Entanglement Routing (OER) scheme which determines the entanglement paths for each request when it arrives. In addition, OER pursues work conservation and fairness among all requests in the QDNs. Through extensive simulations, we demonstrate that OER not only outperforms two representative heuristics by up to 61.27% and 52.79%, respectively, in terms of average request completion time, but also achieves a better fairness performance than these two counterparts.
As quantum computers and quantum networks become more capable, it allows for the possibility to use multiple quantum computers as part of a distributed system. Such a distributed system will have applications such as running quantum algorithms in a distributed fashion [7], leadership elections without communication [7], clock synchronisation [10], and a cryptographic protocol called quantum key distribution [1], etc. However, to create a reliable system, it is important that the underlying quantum network can reliably support the necessary communication protocols between quantum nodes. To support reliable communication in a quantum network, quantum routing algorithms - which are algorithms that plan out how to send qubits and over which subset of nodes in the network - is an active area of research. However, various design choices and algorithms exist that are developed without a realistic simulated environment that can provide rich data that can further help develop, improve, and test these algorithms. Such an environment is important because general-purpose algorithms need to take into account detailed information about how the qubit changes over the communication process - as that requirement can vary for different applications - rather than simpler probability based loss models existing algorithms were developed with. Using existing lower-level tools, we are creating a tool will help evaluate and design routing protocol by providing a variety of models - from simple to complex - to support various stages of development, as well as the ability to generate useful data to evaluate how the protocols perform in a realistic quantum network.
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.