Abstract Towards offering efficient optical networks with regards to the cost and delay, the adaptation of quantum and classical communications can offer a solution to reduce high generated cost of implementing the bare quantum repeaters-based networks. In this paper, the performance of hybrid (classical-Quantum) networks that uses quantum repeaters is analysed and compared with bare quantum repeater network. In a distance, these repeaters are removed and replaced with classical base station. Several network metrics have been evaluated after modelling both quantum and hybrid networks, such as the latency, data rate, energy efficiency, scalability, power consumption and cost of implementation. The results show that the hybrid networks can offer faster connectivity, reduced cost, less required cost of operation and higher scalability. In contrary, the bare quantum repeater network showed higher data rate and higher energy efficiency.
Abstract Towards offering efficient optical networks with regards to the cost and delay, the adaptation of quantum and classical communications can offer a solution to reduce high generated cost of implementing the bare quantum repeaters-based networks. In this paper, the performance of hybrid (classical-Quantum) networks that uses quantum repeaters is analysed and compared with bare quantum repeater network. In a distance, these repeaters are removed and replaced with classical base station. Several network metrics have been evaluated after modelling both quantum and hybrid networks, such as the latency, data rate, energy efficiency, scalability, power consumption and cost of implementation. The results show that the hybrid networks can offer faster connectivity, reduced cost, less required cost of operation and higher scalability. In contrary, the bare quantum repeater network showed higher data rate and higher energy efficiency.
Purpose of the study: systematization and critical analysis of existing approaches to error suppression in quantum repeaters, as well as to assess their advantages and limitations for the implementation of scalable quantum networks and the quantum internet. Methods of research: the paper provides a detailed analysis of modern literature, including a comparison of various quantum repeater schemes, as well as an assessment of resource costs and performance. Result(s): quantum repeaters can be divided into three generations, each of which demonstrates optimal efficiency under certain conditions. The first generation, implementing probabilistic error suppression by generating heralded entanglement and two-way entanglement distillation, is easy to implement and provides the basic functionality of a quantum network, but requires significant time due to the need to exchange classical signals and long-term storage of quantum states. The second generation combines probabilistic entanglement generation with deterministic operation error suppression using quantum error correction, which reduces the requirements for long-term quantum memory, although the exchange of classical signals between neighboring nodes remains mandatory. The third generation relies entirely on deterministic error suppression using one-way classical communication, which allows for a significant reduction in time delays and high entanglement generation rates, despite the need for a denser arrangement of repeaters and high-quality local gates. In addition, the review covers new areas such as memoryless repeaters and all-photonic repeaters. The conducted comparative analysis of resource costs demonstrates that optimization of repeater operating parameters is a key factor for the implementation of scalable quantum networks, which is of direct importance for quantum key distribution, quantum metrology, and distributed quantum computing. Scientific novelty: the scientific novelty lies in the integration of disparate approaches to the implementation of quantum repeaters into a single holistic representation, which allows for an objective assessment of their efficiency by key parameters. The review highlights the potential for new classes of repeaters, such as memoryless repeaters and all-photonic circuits, to become important elements in the development of a quantum internet.
Quantum computing can provide a solution for many problems that classical communication networks encounter, but the knowledge gap between these two is not bridged yet. Accordingly, this paper has proposed directions, evaluations, and futuristic quantum solutions to cloud-based cellular communications. This paper shows the effect of using quantum entanglement phenomena upon the classical cloud network, particularly using an entanglement theory to decrease the enlarged signaling cost delay that the traditional cloud network faces. Through modeling the latency of both paradigms, this paper promises a delay reduction when adapting a quantum method into the mobile cloud networks. This paper also models the power consumption (PC) and energy efficiency of the traditional and quantum-based cloud networks. This paper also shows, via modeling the PC, that installing a quantum-based paradigm is not a power costly method; rather, it shows identical power and energy efficiency figures with a possibility of improvement.
Satellite optical links may be able to extend quantum communication range beyond that which is possible through optical fibres which are constrained by exponential loss scaling. Quantum repeaters have been proposed to mitigate high channel losses in both fibre and satellite links. Although satellite quantum repeaters could improve entanglement distribution efficiency, the attempt rate is constrained by classical communication latency in the entanglement swapping step. Direct entanglement distribution does not suffer this latency and can therefore compensate for high dual-downlink losses by increasing the source rate. A systematic comparative analysis of repeater-assisted and direct entanglement distribution rates using a satellite is absent from the literature. In addition to entanglement distribution rates, a detailed analysis of the fidelity of entanglement distributed by repeater-assisted satellite links has yet to be performed. Here, we develop an in-depth framework for describing a space quantum link consisting of a single satellite and two ground stations. We compare the entanglement distribution rates of direct and repeater-assisted satellite entanglement distribution, taking into account variations in overpass geometry and quantum memory capacity. The long-term entanglement distribution performance to different pairs of major cities is also considered, and the altitudinal dependence is explored. Furthermore, we develop a Monte Carlo model of the repeater satellite to explore the effect that different memory management policies and capacities have on the waiting time statistics of memory qubits. From these statistics we calculate the fidelity distributions of the entangled pairs established between the ground stations. These results will inform mission design for future space-borne quantum repeater nodes, as well as requirements on space-based memory platforms.
Emerging communication systems are expected to integrate new types of communication networks including quantum networks. In contrast to classical networks, the communication in quantum networks is accomplished with qubits and their attribute entanglement. Entanglement is a type of correlation between multiple qubits with no counterpart in classical communication. With the help of entanglement new protocols are developed to perform classical and quantum network tasks more efficiently. The main task of quantum networks is to share entanglement to distant communication partners with the help of intermediate nodes and repeated entanglement swapping, the so called Repeater Protocol. Due to the decoherence of quantum states, establishing entanglement has to be accomplished with minimal delay to preserve the states of qubits. This paper proposes a new Repeater Protocol FRP, which reduces delay by up to 51% and on average by 13% in establishing end-to-end entanglement compared with the direct approach CRP. Additionally, the provided solution lowers hardware requirements for quantum routers. Both protocols, CRP and FRP are evaluated in terms of end-to-end delay and fidelity in extensive simulations with a parameter search on 3 different topologies.
Quantum repeater-based communication over standard single-mode fibre (SMF) is fundamentally constrained by attenuation and propagation delay. Recent advances in hollowcore fibre (HCF) offer significantly lower loss and higher propagation speed, making it a promising alternative, although nearterm deployment remains economically demanding. In this work, we investigate linear repeater architectures in the context of emerging HCF technology. We propose an evaluation framework that combines performance analysis with a cost-efficiency metric and examine three architectures: a homogeneous repeater chain, a three-node hybrid SMF-HCF configuration, and a metro-access hybrid design. All architectures are evaluated using the NetSquid simulation platform. Our results show that partial HCF deployment can significantly enhance secret key rate (SKR) in specific regimes. Furthermore, for homogeneous repeater chains, HCF-based deployments improve both performance and cost efficiency in most explored scenarios. These findings reveal key design trade-offs and provide practical guidelines for HCF integration in future quantum networks.
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.