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 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 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 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.
When built, quantum repeater networks will require classical network protocols to control the quantum operations. However, existing work on repeaters has focused on the quantum operations themselves, with less attention paid to the contents, semantics, ordering and reliability of the classical control messages. In this work we define and describe our implementation of the classical control protocols. The state machines and packet sequences for the three protocol layers are presented, and operation confirmed by running the protocols over simulations of the physical network. We also show that proper management of the resources in a bottleneck link allows the aggregate throughput of two end-to-end flows to substantially exceed that of a single flow. Our layered architectural framework will support independent evolution of the separate protocol layers. Networks of quantum repeaters utilize three concepts to execute a distributed algorithm that creates entangled quantum states between nodes that are far apart: a basic entanglement mechanism which depends on the physical implementation, error management (in this work, we study a method known as purification), and finally a quantum state propagation layer (here we implement entanglement swapping, which builds multi-hop connections from single-hop connections). Some researchers are investigating approaches that are substantially different from entanglement swapping [30, 24, 19]. Here we focus on swapping, but the layered architecture approach is broadly applicable, allowing other implementations to replace only a single layer in the protocol stack. Previous work primarily focused on the physical and mathematical tools for building repeaters. Classical information is also needed to enable teleportation and swapping, as many quantum operations are not deterministic, and results of quantum measurements need to be reported to distant partners before further operations can proceed. Also, operations in the middle of the network must be coordinated to route and swap properly. This requires classical messages to make operations robust, but message propagation times penalize performance. Even though this delay is usually included in repeater simulations, prior work has not defined the protocols in detail, especially with respect to how all of the nodes make consistent decisions in a timely fashion. In this work, we introduce a protocol stack for networks of quantum repeaters that considers all the necessary classical messages and which can be easily adapted for different approaches at all three protocol layers. We run simulations of competing flows on a dumbbell topology in order to increase our confidence in the behavior of our network protocols. By adjusting the fidelity thresholds required for entanglement swapping, we show that some configurations boost the aggregate throughput for multiple flows significantly above the maximum for a single flow, taking advantage of resources that would otherwise sit idle. The operation of such complex networks and such delicate tuning of the system without formal protocol definitions would not be possible. Previous work has also concentrated almost exclusively on the dedicated use of a single line or chain of repeaters, delivering Bell pairs only to the two nodes at the ends of the chain. Networks, however, typically have more than two end points, and allow any pair of these end nodes to communicate. More topologically complex networks, with numerous end nodes, are obviously much more scalable than connecting every possible pair of nodes using a dedicated line of repeaters. we investigate how classical multiplexing schemes translate to the domain of quantum repeaters, in order to manage shared resources and active communication flows of data from different stations. We simulate four sharing protocols in a complex network with competing traffic. Circuit switching gives any individual flow the best performance, but makes poor use of the overall network and is inflexible. We use circuit switching as our baseline case to compare time division multiplexing, buffer space multiplexing, and statistical multiplexing, and show that all multiplexing schemes are better than circuit switching. For the particular network simulated, we find that statistical multiplexing outperforms time division multiplexing by 28% and buffer space multiplexing by 13%. We find that all three multiplexing schemes are fair; each flow is penalized a similar percentage of its throughput as the the total number of users in the network increases. Finally, statistical multiplexing requires no network-wide coordination of the use of quantum memory or channels, and is easier to implement than a robust, scalable scheme for the other protocols. Our current results suggest that the best strategy for quantum repeater networks is statistical multiplexing. (This is in fact the quantum analogue of the basis on which the Internet works.) However, our current simulations are done with no degradation of memory over time, using the assumption of quantum error-corrected memory at each repeater; inclusion of decoherence and a finite qubit lifetime remains as future work.
This paper proposes a novel approach to distributed memory leveraging the unique properties of quantum entanglement. The core claim is that entanglement can enable long-range, low-latency, and high-capacity distributed memory, effectively bypassing the limitations of traditional network-based data transfer. The proposed mechanism involves a distributed storage system built upon Quantum Key Distribution (QKD) principles. Each node in the system stores a portion of the overall data, and entanglement between quantum bits (qubits) is utilized to establish correlations. By performing measurements and operations on these entangled states, data access and updates can be achieved rapidly and securely across geographically separated nodes. This work addresses the significant challenges inherent in maintaining high-fidelity entanglement and developing efficient entanglement manipulation protocols for large-scale quantum networks. The theoretical framework presented here outlines a foundational architecture for this emerging technology.
The Quantum Internet, a network interconnecting remote quantum devices through quantum links in synergy with classical ones, is envisioned as the final stage of the quantum revolution, opening fundamentally new communications and computing capabilities. But the Quantum Internet is governed by the laws of quantum mechanics. Phenomena with no counterpart in classical networks, such as no-cloning, quantum measurement, entanglement and quantum teleportation, impose new challenging constraints for network design. Specifically, classical network functionalities are based on the assumption that classical information can be safely read and copied. However, this assumption does not hold in the Quantum Internet. As a consequence, its design requires a major network-paradigm shift to harness the quantum mechanics specificities. The goal of this work is to shed light on the challenges and open problems of Quantum Internet design. We first introduce some basic knowledge of quantum mechanics, needed to understand the differences between a classical and a quantum network. Then, we introduce quantum teleportation as the key strategy for transmitting quantum information without physically transferring the particle that stores the quantum information or violating the principles of quantum mechanics. Finally, the key research challenges to design quantum communication networks are discussed.