Abstract In this paper, the key challenges (loss due to distance, entanglement routing, multi‐commodities) for the coming quantum internet, relying on entanglement of quantum bits (for short, qubits) on top of an existing network, are analyzed. A unifying framework enabling to compare the various entanglement distribution, purification, and routing protocols published so far is presented. With regard to entanglement routing, the introduction of different time windows will be essential in order to cope efficiently with the main challenges like complex route calculation and fidelity estimation on the one hand, actual entanglement route selection and entangled photon generation on the other hand. For a roll‐out on top of existing transmission networks, all the research publications for the last 20 years start to cover pretty well the global scheme. Nevertheless, open questions remain, like the actual advantage of some task execution prior to the online quantum path selection, or the design of algorithms approximating the multi‐commodities flow optimization problem, or the issue of dealing with a processing time not much longer than the qubit life time.
Abstract In this paper, the key challenges (loss due to distance, entanglement routing, multi‐commodities) for the coming quantum internet, relying on entanglement of quantum bits (for short, qubits) on top of an existing network, are analyzed. A unifying framework enabling to compare the various entanglement distribution, purification, and routing protocols published so far is presented. With regard to entanglement routing, the introduction of different time windows will be essential in order to cope efficiently with the main challenges like complex route calculation and fidelity estimation on the one hand, actual entanglement route selection and entangled photon generation on the other hand. For a roll‐out on top of existing transmission networks, all the research publications for the last 20 years start to cover pretty well the global scheme. Nevertheless, open questions remain, like the actual advantage of some task execution prior to the online quantum path selection, or the design of algorithms approximating the multi‐commodities flow optimization problem, or the issue of dealing with a processing time not much longer than the qubit life time.
The quantum internet is a global system also called the future internet and is considered a complement to the classical packet switching internet, which performs the function of exchanging messages in the network in an innovative way, as it depends on the basic principles of quantum bits. In order to prepare for the quantum internet, its protocols must be configured initially like routing protocols, and because routing in the quantum internet depends mainly on the property of quantum entanglement, it is facing a constant challenge to what the quantum properties impose, Accordingly, studies in this field continue to emerge, as proposals for protocols are renewed. Therefore, in this research, we present a comprehensive study of the recently proposed quantum routing protocols by classifying these protocols into two categories, the first deals with the routing metrics on which the protocol depends, while the other deals with the problem being solved through the routing protocol. It is shown that although many metrics were suggested for routing protocols, the common metric was the throughput (entanglement rate), In addition, it was considered an essential metric in solving most of the routing problems in quantum networks.
Quantum computing is a new discipline that uses the ideas of quantum physics to do calculations that are not possible with conventional computers. Quantum bits, called qubits, could exist in superposition states, making them suitable for parallel processing in contrast to traditional bits. When it comes to addressing complex challenges like proof simulation, optimization, and cryptography, quantum entanglement and quantum interference provide exponential improvements. This survey focuses on recent advances in entanglement routing, quantum key distribution (QKD), and qubit management for short- and long-distance quantum communication. It studies optimization approaches such as integer programming, reinforcement learning, and collaborative methods, evaluating their efficacy in terms of throughput, scalability, and fairness. Despite improvements, challenges remain in dynamic network adaptation, resource limits, and error correction. Addressing these difficulties necessitates the creation of hybrid quantum–classical algorithms for efficient resource allocation, hardware-aware designs to improve real-world deployment, and fault-tolerant architecture. Therefore, this survey suggests that future research focus on integrating quantum networks with existing classical infrastructure to improve security, dependability, and mainstream acceptance. This connection has significance for applications that require secure communication, financial transactions, and critical infrastructure protection.
We present an approach to purification and entanglement routing on complex quantum network architectures, that is, how a quantum network equipped with imperfect channel fidelities and limited memory storage time can distribute entanglement between users. We explore how network parameters influence the performance of path-finding algorithms necessary for optimizing routing and, in particular, we explore the interplay between the bandwidth of a quantum channels and the choice of purification protocol. Finally, we demonstrate multi-path routing on various network topologies with resource constraints, in an effort to inform future design choices for quantum network configurations. Our work optimizes both the choice of path over the quantum network and the choice of purification schemes used between nodes. We consider not only pair-production rate, but optimize over the fidelity of the delivered entangled state. We introduce effective heuristics enabling fast path-finding algorithms for maximizing entanglement shared between two nodes on a quantum network, with performance comparable to that of a computationally-expensive brute-force path search.
The efficacy of a communication network hinges upon both its physical architecture and the protocols that are employed within it. In the context of quantum communications, there exists a fundamental rate-loss trade-off for point-to-point quantum channels such that the rate for distributing entanglement, secret keys, or quantum states decays exponentially with respect to transmission distance. Quantum networks are the solution to overcome point-to-point limitations, but they simultaneously invite a challenging open question: How should quantum networks be designed to effectively and efficiently guarantee high rates? Now that performance and physical topology are inexorably linked, this question is not easy, but the answer is essential for a future quantum internet to be successful. In this work, we offer crucial insight into this open question for complex optical-fiber quantum networks. Using realistic descriptions of quantum networks via random network models and practical end-to-end routing protocols, we reveal critical phenomena associated with large-scale quantum networks. Our work reveals the weaknesses of applying single-path routing protocols within quantum networks, observing an inability to achieve reliable rates over long distances. Adapting algorithms for multipath routing, we employ an efficient and practical multipath routing algorithm capable of boosting performance while minimizing costly quantum resources.
ABSTRACT The rapid growth of global data traffic and the increasing demand for secure and scalable communication are driving the need for networking paradigms beyond the classical internet. The quantum internet has emerged as a promising solution, leveraging the principles of quantum mechanics to enable intrinsically secure communication, and computation. In this paper, we present a comprehensive review of the fundamental building blocks and system architectures required for large‐scale quantum networks, with a particular focus on photonic hardware platforms. We introduce key concepts of quantum information relevant to networking, including qubits, entanglement, and decoherence, and examine enabling technologies across different qubit platforms, highlighting photonic qubits as the primary carriers for long‐distance communication. We review major deterministic and probabilistic entanglement generation techniques, and analyze entanglement distribution strategies based on fiber, satellite, and quantum repeater architectures. Beyond the physical layer, we provide a system‐level perspective on quantum networking through protocol stack design, as well as challenges in entanglement routing, forwarding, and scheduling. Finally, we discuss experimental testbeds for entanglement distribution in both fiber‐based and free‐space systems, and outline the corresponding challenges and future research directions, including satellite‐assisted architectures for achieving scalable and globally connected quantum networks.
Over the course of the last five decades, there has been substantial growth in conventional network routing design, transitioning from small static node networks to vast systems connecting billions of devices. This evolution has been facilitated by the separation of concerns principle, which involves integrating network functionalities into graph or random network designs and utilizing specific protocols to enable diverse communication capabilities. The landscape of quantum networks is rapidly evolving, presenting new paradigms in information transmission and processing. Routing protocols play a pivotal role in establishing efficient communication pathways within quantum networks, enabling the transmission of quantum states and entanglement across interconnected nodes. The objective of this paper is to shed light on existing entanglement routing design techniques within quantum networks. The design of quantum entanglement routing necessitates a departure from conventional network protocols due to its unique considerations of quantum entanglement and entanglement swapping. However, the implementation of these techniques is fraught with significant challenges, including quantum system decoherence and noise, limitations on communication ranges, and the need for specialized hardware. The paper initiates by surveying critical research in quantum routing design techniques, then delves into essential aspects of the routing concept, associated quantum operations, and the step-wise process for establishing efficient and resilient quantum networks. In summary, this paper provides an overview of the current landscape of quantum entanglement routing techniques. It outlines their core principles, protocols, and challenges, while also highlighting potential applications and charting future directions for research and development.