The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.
The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.
Quantum cryptography uses the quantum properties of individual photons to provide two or more users with means to communicate securely and efficiently. Specifically, quantum key distribution (QKD) focuses on the secure communication between two distant parties and guarantees the security of a transmitted message between them. Although QKD is the most mature application of quantum cryptography, applications of quantum mechanics in communication systems are not limited to QKD and other cryptographic protocols can be implemented as well. This thesis focuses on the implementation of quantum cryptographic systems over deployed fiber. A first QKD system was built and used to demonstrate the BB84 protocol over deployed fiber between the University of Calgary and SAIT. The system implemented a novel tool called quantum frames that allow for the quantum signals to be routed, for clock synchronization, and for channel stabilization in a network scenario. The same system was used to examine the scalability of the secret key generation rate in different steps of the process in order to detect potential bottlenecks for key generation rate of high speed systems. A second QKD system was developed to demonstrate the measurement-device independent QKD protocol. The system worked over deployed fiber between the University of Calgary, SAIT, and Foothills Hospital in the City of Calgary. The advantage of the measurement-device independent QKD protocol over previous QKD protocols is that it eliminates the possibility of side-channel attacks that target single photon detectors used in QKD systems. This demonstration also involved the first demonstration of a Bell state measurement over deployed fiber. Bell state measurements were further studied by using novel single photon detectors, which allowed demonstrating a highly efficient Bell measurement. Finally, a cryptographic protocol known as private queries was demonstrated between the University of Calgary and SAIT. Quantum private queries were demonstrated for the first time over deployed fiber by developing and implementing an error correction scheme to make the protocol noise and loss tolerant.
Quantum cryptography uses quantum mechanical principles to provide a new level of security to communication networks. This paper describes an advanced system that will provide scalable, cost-effective quantum key distribution (QKD) through the incorporation of quantum and classical infrastructure in a resilient system that will increase data security. The current distance, device vulnerablity and interoperability problems are solved with our proposed model, which supports the usage of entanglement-based repeaters, AI algorithms to manage the keys and MDI-QKD protocols. Owing to its strong resistance to environmental noise and practical attacks, the scheme is suitable for deployment under practical communication environments. Both the experimental verification and the theoretical modeling show a clear enhancement both in security and transmission distance.
Quantum Key Distribution (QKD) constitutes one of the most profound practical applications of quantum mechanics, enabling two parties to exchange cryptographic keys whose security is guaranteed by the fundamental laws of physics rather than the assumed computational hardness of mathematical problems. As quantum computing capabilities continue to advance, classical public-key infrastructure faces an existential threat, rendering QKD a critical component of post-quantum secure communication architectures. This paper presents a comprehensive survey of QKD spanning foundational protocols, rigorous security proofs, hardware implementation challenges, deployment experiences across metropolitan fiber networks, and recent satellite-based experiments. We analyze the BB84, E91, B92, SARG04, continuous-variable, measurement-device-independent (MDI-QKD), and twin-field (TF-QKD) protocols in depth, examining their security assumptions, achievable key rates, and practical limitations. Particular attention is given to side-channel vulnerabilities in realistic implementations, decoy-state methods for mitigating photon-number-splitting attacks, and finite-key security analysis. We review key performance benchmarks from commercial systems and discuss integration with classical network infrastructure. The paper concludes by identifying open challenges in quantum repeater development, satellite QKD scalability, and standardization efforts essential for large-scale deployment.
Abstract Quantum key distribution (QKD) enables information-theoretically secure communication based on the laws of quantum physics. Although QKD remains an active area of research, ongoing commercialization efforts underscore its growing significance in modern physics and communication. This mini-review provides a brief overview of existing multi-user QKD networks and ongoing developments, with an emphasis on field tests. We examine different network architectures. In addition, we explore the prospect of photonic integrated circuits (PICs) and their current capabilities in QKD implementations. We also present various post-processing algorithms focusing on error correction (EC) and privacy amplification (PA), as well as implementations of these protocols in different experiments. Finally, we conclude by providing an overview of our quantum network and discussing setup choices from our recent field tests.
This paper describes trends in the field of encryption, based on the principles of quantum cryptography. Here is a description of commercial self-compensation quantum key distribution system (QKDS). A description of quantum-cryptographic network stand, based on integrated commercial QKDS Clavis2 from idQuantique (Switzerland), is also proposed. Research of quantum key integration into telecommunication data transmission network encryption protocol is offered. Capabilities of quantum-cryptographic network stand are also formulated.
Since it was noted that quantum computers could break public key cryptosystems based on number theory, extensive studies have been undertaken on Quantum Key Distribution (QKD). QKD or Quantum Cryptography solves the key distribution problem by allowing the exchange of a cryptographic key between two remote parties with absolute security, guaranteed by the laws of physics. Actually, the progress of research in this field allows the implementation of Quantum Cryptography outside of laboratories. Efforts are made to exploit this technology in the existing communication networks and to improve the performance and reliability of the implemented technologies. The cryptosystems based on QKD are very promising and also the technology is improving more and more to fulfill requirements. In this paper, we provide a state-of-the-art of practical Quantum Cryptography by exposing the popular works and projects on QKD implementation.