Quantum key distribution (QKD) is an innovative technology allowing information-theoretically-secure key sharing among distant users relying only on fundamental rules of quantum physics, without assumptions about the computational power of the attacker [1]. Different variants of this technology are making their way into the market since several years and QKD testbeds are under deployment worldwide, for institutional and commercial use. Among the remaining challenges, its integration in existing infrastructure is a vital one, together with the hybridization with different technologies.
Quantum key distribution (QKD) is an innovative technology allowing information-theoretically-secure key sharing among distant users relying only on fundamental rules of quantum physics, without assumptions about the computational power of the attacker [1]. Different variants of this technology are making their way into the market since several years and QKD testbeds are under deployment worldwide, for institutional and commercial use. Among the remaining challenges, its integration in existing infrastructure is a vital one, together with the hybridization with different technologies.
Quantum key distribution (QKD) is a technology that allows sharing secret cryptographic keys between two distant users (Alice and Bob), whose intrinsic security is guaranteed by fundamental principles of quantum mechanics. QKD is a mature technology: in Europe, all the 27 EU member states are working in a European Commission initiative (EuroQCI) to design, develop and deploy a quantum communication infrastructure composed by several national networks. For example, in Italy, the Italian Quantum Backbone will be used as a quantum communication testbed within the project QUID, that is in charge of the realization of the Italian part of EuroQCI.
Quantum Key Distribution (QKD) supports the negotiation and sharing of private keys with unconditional security between authorized parties. Over the years, theoretical advances and experimental demonstrations have successfully transitioned QKD from laboratory research to commercial applications. As QKD expands its reach globally, it encounters challenges such as performance limitations, cost, and practical security concerns. Nonetheless, innovations in satellite-based QKD and the development of new protocols are paving the way towards a worldwide network. In this review, we provide an overview of QKD implementations, with a focus on protocols, devices, and quantum channels. We discuss the challenges of practical QKD and explore long-haul QKD. Additionally, we highlight the future research directions that are expected to significantly advance the realization of a global QKD network.
Abstract Quantum key distribution (QKD) provides in principle unconditional security of key sharing based on the laws of physics only. In the last decade, several experimental and commercial QKD networks have been built and operated worldwide. Demonstrational applications of QKD in financial institutions, government networks, and critical infrastructures such as the power grid have been initially explored. However, large-scale deployment and full-scale commercialization of QKD networks still faces some technological and standardisation challenges. In this paper, recent developments and in-field deployments of QKD networks are reviewed and advancements in QKD standardisation are also discussed.
Quantum technology, and especially quantum computing, is advancing rapidly. Our every-day secure communication infrastructure relies heavily on public key cryptography; unfortunately, many public key schemes are in fact insecure against quantum algorithms. Furthermore, adversaries who, today, capture information encrypted using classical key distribution systems, can wait and, as soon as quantum computers of sufficient power become available, they may decipher all previously captured information. While some new “post-quantum” public key systems are assumed to be secure against quantum computers, this is only an assumption and, even if the assumption remains valid, still results in systems that are less efficient for end-users than the more commonly used public key systems employed today. While the advent of quantum technology may seem detrimental to security, in fact, one may harness the power of quantum through quantum key distribution (QKD) for stronger security guarantees. Such QKD protocols allow two (or more) parties to establish a shared secret key, secure against an all-powerful adversary. Perhaps surprising is that QKD technology is already here both experimentally and commercially. This tutorial serves as an introduction to basic QKD along with QKD technology from a practical perspective. Quantum communication is a highly interdisciplinary field of research and one of the goals of this article is to introduce a larger set of researchers and practitioners to its study in the hopes of furthering its progress and eventual wide-scale adoption.
In a society based on the continuous exchange of sensitive data and information, the importance of secure and trustful communications is essential. Quantum key distribution (QKD) makes it possible to share data in an unconditionally secure way exploiting the basic principles of Quantum Mechanics [1]. During the last 30 years, many QKD protocols have been developed and tested, achieving long distance transmission [2] and secret key rates up to hundreds of Mbits per second [3]. However, this technology is still far from a large-scale deployment in existing fiber networks and telecom infrastructures, due to multiple factors: low secret-key rate, limited distance between users, lack of applications, high costs and high requirements in terms of low noise fiber links.
Quantum Key Distribution (QKD) is a mechanism for ensuring secure key exchange based on the fundamental principles of quantum mechanics. It has evolved significantly over the past four decades. QKD networks have evolved from experiments to large-scale deployments, enabling longer transmission distances and enhanced security performance. Existing information security relies on modern cryptographic primitives such as Elliptic Curve Diffie–Hellman (ECDH), RSA, and AES. Although AES-256 is considered quantum-resistant, ECDH and RSA cannot withstand attacks by a specific quantum computer. Specifically, with enough quantum bits, Shor’s and Grover’s algorithms can break RSA and ECDH through rapid integer factorization and quantum search capabilities, respectively. Consequently, QKD offers a promising method towards information-theoretic security, using trusted nodes, optical routers, and future quantum repeaters. However, completely replacing current infrastructure with QKD systems is both costly and impractical. Thus, existing QKD can be integrated into current infrastructure, including dark fiber and satellite systems. Previous surveys have primarily focused on isolated aspects such as fiber-based QKD, free-space QKD, or theoretical Internet architectures. There is a lack of a comprehensive survey that simultaneously presents fundamentals, QKD protocols and security, network implementations, and experimental advances. This makes it difficult for readers to grasp the full scope of the field. This survey focuses on QKD from the ground up, covering the essential foundations of QKD, exploring various QKD protocols, concerning different types of attacks, reviewing real-world QKD network deployments, and highlighting challenges and future directions.