The problem of entanglement routing in quantum networks has found much interest in recent times. Phased protocols have been proposed wherein the entire process of routing and establishment of end-to-end entanglement between nodes of a quantum network is accomplished in phased time-slots. Examples of such protocols are Q-PASS and Q-CAST [Shi et al. Concurrent Entanglement Routing for Quantum Networks: Model and Designs. (IEEE/ACM Transactions on Networking, 32(3):2205–2220, 2024)].In this work, our contribution is two-fold. We design, implement and make available an extensible tool called QPhase that will help quantum network routing protocol designers implement and analyze against various metrics, their (synchronous and phased) protocols.Secondly, we propose a hybrid protocol called Q-CAST-Enhanced that uses the best features of the Q-PASS and Q-CAST protocols. In addition, the protocol incorporates the capability of learning from historical patterns and being adaptive to network changes. Q-CAST-Enhanced uses a hybrid path selection strategy wherein the expected throughput metric is combined with a newly introduced metric called reliability, which is responsible for accounting for historical success. The protocol also employs an adaptive recovery mechanism that dynamically switches between the XOR-based and segment-based recovery methods based on path information. We report simulation results for Q-CAST-Enhanced along with comparisons with Q-CAST using our simulator, QPhase.
The problem of entanglement routing in quantum networks has found much interest in recent times. Phased protocols have been proposed wherein the entire process of routing and establishment of end-to-end entanglement between nodes of a quantum network is accomplished in phased time-slots. Examples of such protocols are Q-PASS and Q-CAST [Shi et al. Concurrent Entanglement Routing for Quantum Networks: Model and Designs. (IEEE/ACM Transactions on Networking, 32(3):2205–2220, 2024)].In this work, our contribution is two-fold. We design, implement and make available an extensible tool called QPhase that will help quantum network routing protocol designers implement and analyze against various metrics, their (synchronous and phased) protocols.Secondly, we propose a hybrid protocol called Q-CAST-Enhanced that uses the best features of the Q-PASS and Q-CAST protocols. In addition, the protocol incorporates the capability of learning from historical patterns and being adaptive to network changes. Q-CAST-Enhanced uses a hybrid path selection strategy wherein the expected throughput metric is combined with a newly introduced metric called reliability, which is responsible for accounting for historical success. The protocol also employs an adaptive recovery mechanism that dynamically switches between the XOR-based and segment-based recovery methods based on path information. We report simulation results for Q-CAST-Enhanced along with comparisons with Q-CAST using our simulator, QPhase.
Quantum entanglement enables important computing applications such as quantum key distribution. Based on quantum entanglement, quantum networks are built to provide long-distance secret sharing between two remote communication parties. Establishing a multi-hop quantum entanglement exhibits a high failure rate, and existing quantum networks rely on trusted repeater nodes to transmit quantum bits. However, when the scale of a quantum network increases, it requires end-to-end multi-hop quantum entanglements in order to deliver secret bits without letting the repeaters know the secret bits. This work focuses on the entanglement routing problem, whose objective is to build long-distance entanglements via untrusted repeaters for concurrent source-destination pairs through multiple hops. Different from existing work that analyzes the traditional routing techniques on special network topologies, we present a comprehensive entanglement routing model that reflects the differences between quantum networks and classical networks as well as a new entanglement routing algorithm that utilizes the unique properties of quantum networks. Evaluation results show that the proposed algorithm Q-CAST increases the number of successful long-distance entanglements by a big margin compared to other methods. The model and simulator developed by this work may encourage more network researchers to study the entanglement routing problem.
Quantum entanglement enables important computing applications such as quantum key distribution. Based on quantum entanglement, quantum networks are built to provide long-distance secret sharing between two remote communication parties. Establishing a multi-hop quantum entanglement exhibits a high failure rate, and existing quantum networks rely on trusted repeater nodes to transmit quantum bits. However, when the scale of a quantum network increases, it requires end-to-end multi-hop quantum entanglements in order to deliver secret bits without letting the repeaters know the secret bits. This work focuses on the entanglement routing problem, whose objective is to build long-distance entanglements via untrusted repeaters for concurrent source-destination pairs through multiple hops. Different from existing work that analyzes the traditional routing techniques on special network topologies, we present a comprehensive entanglement routing model that reflects the differences between quantum networks and classical networks as well as a new entanglement routing algorithm that utilizes the unique properties of quantum networks. Evaluation results show that the proposed algorithm Q-CAST increases the number of successful long-distance entanglements by a big margin compared to other methods. The model and simulator developed by this work may encourage more network researchers to study the entanglement routing problem.
Entanglement routing in near-term quantum networks consists of choosing the optimal sequence of short-range entanglements to combine through swapping operations to establish end-to-end entanglement between two distant nodes. Similar to traditional routing technologies, a quantum routing protocol uses network information to choose the best paths to satisfy a set of end-to-end entanglement requests. However, in addition to network state information, a quantum routing protocol must also take into account the requested entanglement fidelity, the probabilistic nature of swapping operations, and the short lifetime of entangled states. In this work, we formulate a practical entanglement routing problem and analyze and categorize the main approaches to address it, drawing comparisons to, and inspiration from, classical network routing strategies where applicable. We classify and discuss the studied quantum routing schemes into reactive, proactive, and hybrid routing.
Quantum networks enable a number of important applications such as quantum key distribution. The basic function of a quantum network is to enable long-distance quantum entanglement between two remote communication parties. This work focuses on the entanglement routing problem, whose objective is to build long-distance entanglements for the concurrent source-destination pairs through multiple hops. Different from existing works that analyzes the traditional routing techniques on special network topologies, we present a comprehensive entanglement routing model that reflects the differences between quantum networks and classical networks and new entanglement routing algorithms that utilize the unique properties of quantum networks. Evaluation results show that the proposed algorithm Q-CAST increases the number of successful long-distance entanglements by a big margin compared to other methods. The model and simulator developed by this work may encourage more network researchers to study the entanglement routing problem.
The advancement of mobile quantum networks unlocks new opportunities for secure communication in dynamic environments, such as drone-based networks equipped with quantum repeaters. This work introduces Q-CAST Mobility, an adaptation of the Q-CAST quantum routing protocol, specifically optimized for mobile quantum nodes. By integrating concepts from classical reactive and proactive routing protocols, inspired by the Zone Routing Protocol (ZRP), and leveraging Q-CAST’s quantum routing framework, Q-CAST Mobility combines multipath routing, dynamic route updates, and efficient qubit management to maintain robust quantum entanglements in highly mobile scenarios. To assess its performance, we conducted simulations across various mobility levels, comparing Q-CAST Mobility with state-of-the-art methods. The results demonstrate that Q-CAST Mobility significantly outperforms existing protocols regarding throughput, underscoring its efficiency and adaptability in mobile quantum communication networks.
The quantum Internet relies on the ability to distribute entangled quantum bits (ebits) between quantum memories at the end nodes, to perform applications like blind or distributed quantum computing that are impossible if end nodes are connected via a classical, i.e., non-quantum network. This need creates new challenges due to the fragile nature of entanglement, which decoheres over short timescales and cannot be amplified, buffered, or retransmitted. Two broad categories of approaches have been proposed in the scientific literature to realize such an entanglement distribution in a given path: one relying on a synchronous time-slotted model, and another one where intermediate nodes interact asynchronously. However, both of them implicitly assume a serial operation, where one ebit is established and made available to the application on end nodes before creating a new one. This is inefficient in long-range networks, with high transmission latencies, if the intermediate nodes have multiple memory qubits that could be used in parallel. To overcome this limitation, in this paper, we study the implications of multiplexing concurrent ebit requests on the same quantum, for both synchronous and asynchronous operation. Furthermore, for the latter, we define a novel distribution protocol, called HOPPER, where the intermediate nodes make autonomous and hop-by-hop decisions on the use of their local resources when establishing an ebit. With numerical simulations, we show that HOPPER is effective in handling multiple ebit requests in parallel, and it exhibits significantly better performance than a synchronous alternative in different scenarios.