Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Experimental and Theoretical Physics

Concatenation of Keys in Quantum Cryptography: How Quantum Entanglement “Penetrates to” Classical Devices

S. N. Molotkov

Published Oct 1, 2018• 2 citations
Publisher

Abstract

Abstract Quantum mechanics admits collective measurements that are related to the projection onto entangled states and allow one to retrieve more classical information from an ensemble of quantum states compared with individual measurements. In this relation, a fundamental question arises for key secrecy in quantum cryptography. Should the secrecy criterion be formulated with regard to all keys distributed both on previous and future quantum key distribution (QKD) sessions, or it suffices to guarantee key secrecy only in an individual QKD session? The study of this question is the subject of the present paper.

DOI
10.1134/s1063776118090066

Related papers

Quantum entanglement and composite keys in quantum cryptography

S. N. Molotkov

The security of quantum cryptography protocols after a quantum key distribution (QKD) session is formulated in terms of proximity between two situations: quantum states corresponding to real and ideal situations after QKD. The measure of proximity is the trace distance. It is more reasonable to formulate security directly in terms of the smallness of probability of successive guessing of keys by an eavesdropper after an arbitrary number of QKD sessions. There is a fundamental question the answer to which is a priori very unobvious: Is the security criterion in terms of the proximity of the real and ideal situations for a single QKD session sufficient to guarantee the security of keys in terms of the smallness of probability of guessing of keys by the eavesdropper after an arbitrary number of QKD sessions? It has been shown that the answer to this question is positive.

Journal of Experimental and Theoretical Physics Letters•Jun 1, 2017•2 citations

Quantum entanglement and its implications for secure communication

M P Lingaraju, Bharath Kumar T, C Jayachandra

Quantum entanglement is a fundamental and intriguing phenomenon in quantum mechanics, wherein two or more particles become correlated in such a way that the state of one instantaneously influences the state of the other, regardless of the distance separating them. This research delves into the theoretical foundation of quantum entanglement, exploring its mathematical formulation, key experimental validations, and implications for emerging technologies. A primary focus is placed on its application in secure communication, particularly in Quantum Key Distribution (QKD), where entanglement enables fundamentally secure cryptographic protocols resistant to eavesdropping. We present an in-depth analysis of various QKD protocols, including BB84, E91, and decoy-state methods, assessing their security, efficiency, and practical feasibility. Recent experimental advancements in entanglement-based cryptography are examined, alongside real-world implementations and their technical challenges, such as photon loss, decoherence, and scalability in long-distance quantum communication networks. Additionally, we provide comparative insights into the efficiency of different QKD protocols using a bar chart, while figures and tables illustrate core quantum principles and experimental setups. By addressing both theoretical and practical aspects, this study contributes to a comprehensive understanding of quantum entanglement’s role in secure communication and highlights future directions for overcoming existing technological limitations.

World Journal of Advanced Research and Reviews•Feb 28, 2019•0 citations

Quantum Cryptography: A Novel Approach to Secure Communications

Dr. Emily Chen

Quantum cryptography represents a revolutionary paradigm shift in secure communication by leveraging the principles of quantum mechanics to guarantee unbreakable encryption. Unlike classical cryptographic methods dependent on computational hardness, quantum cryptography exploits quantum phenomena such as superposition and entanglement to provide provable security against eavesdropping. This paper explores fundamental quantum cryptographic protocols, their operational principles, and recent advances that enable practical deployment. We further discuss challenges, implementation issues, and the future scope of quantum key distribution (QKD) technologies in securing global communication infrastructures

American Journal Of Cryptography And Network Security•Jun 30, 2024•0 citations

Quantum Cryptography – Principles, Protocols, and Future Directions: A Review

Dian Arif Rachman, Muhamad Akrom, Didik Hermanto +4 more

The rapid advancement of quantum computing poses a significant threat to classical cryptographic systems that rely on the computational hardness of mathematical problems such as integer factorization and discrete logarithm problems. In this context, quantum cryptography has emerged as a promising paradigm for secure communication based on the fundamental principles of quantum mechanics rather than on computational assumptions. This paper presents a comprehensive review of quantum cryptography, with a particular focus on Quantum Key Distribution (QKD), the most mature application. The study discusses the theoretical foundations of quantum security, including superposition, entanglement, and the No-cloning theorem, which collectively enable eavesdropping detection and guarantee information-theoretic security. Furthermore, the review examines major QKD protocols, such as BB84 and E91, as well as their advanced variants designed to address practical vulnerabilities and enhance performance. Recent progress in real-world implementations, including fiber-optic networks, free-space communication, and satellite-based systems such as the Micius satellite, is also analyzed. In addition, the paper highlights critical challenges related to scalability, hardware limitations, and security loopholes arising from imperfect devices. Finally, emerging research directions, including hybrid cryptographic frameworks that integrate quantum and post-quantum approaches, are discussed to provide insights into the future of secure communication. This review aims to provide a structured, up-to-date understanding of quantum cryptography, bridging the gap between theoretical developments and practical implementations, and emphasizing its crucial role in shaping next-generation cybersecurity systems.

Journal of Multiscale Materials Informatics•Jul 3, 2026•0 citations

A Survey on Quantum Key Distribution Protocols

Jasleen Kour, Saboor Koul, Prince Zahid

Quantum cryptography is based on quantum mechanics to guarantee secure communication.It allows two parties to produce a shared random bit string known only to them.These random bits can be used as a key to encrypt and decrypt messages.The most important and unique property of quantum cryptography is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key.It is based on fundamental aspects of quantum mechanics.By using quantum entanglement or quantum super positions and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping.Quantum cryptography is used to produce and distribute a key, not to transmit any message data.This key along with certain encryption algorithm, is used to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel.This paper concentrates on comparison between classical and quantum cryptography as well as survey on various quantum key distribution protocols used to generate and distribute the key among communicating parties.

International Journal on Computational Science & Applications•Jun 30, 2017•2 citations

Entanglement based quantum key distribution: exact analytical solution in the case of detectors efficiency mismatch

S. N. Molotkov

Abstract The paper provides a complete analytical proof of the secrecy of the quantum key distribution for the single-photon quantum states in the case of different quantum efficiency of detectors. Taking into account the imperfect and different quantum efficiency of detectors is fundamentally important for ensuring the secrecy of keys in practical systems of quantum cryptography.

Laser Physics Letters•Mar 2, 2021•10 citations
Abstract Quantum mechanics admits collective measurements that are related to the projection onto entangled states and allow one to retrieve more classical information from an ensemble of quantum states compared with individual measurements. In this relation, a fundamental question arises for key secrecy in quantum cryptography. Should the secrecy criterion be formulated with regard to all keys distributed both on previous and future quantum key distribution (QKD) sessions, or it suffices to guarantee key secrecy only in an individual QKD session? The study of this question is the subject of the present paper.
The security of quantum cryptography protocols after a quantum key distribution (QKD) session is formulated in terms of proximity between two situations: quantum states corresponding to real and ideal situations after QKD. The measure of proximity is the trace distance. It is more reasonable to formulate security directly in terms of the smallness of probability of successive guessing of keys by an eavesdropper after an arbitrary number of QKD sessions. There is a fundamental question the answer to which is a priori very unobvious: Is the security criterion in terms of the proximity of the real and ideal situations for a single QKD session sufficient to guarantee the security of keys in terms of the smallness of probability of guessing of keys by the eavesdropper after an arbitrary number of QKD sessions? It has been shown that the answer to this question is positive.
Quantum entanglement is a fundamental and intriguing phenomenon in quantum mechanics, wherein two or more particles become correlated in such a way that the state of one instantaneously influences the state of the other, regardless of the distance separating them. This research delves into the theoretical foundation of quantum entanglement, exploring its mathematical formulation, key experimental validations, and implications for emerging technologies. A primary focus is placed on its application in secure communication, particularly in Quantum Key Distribution (QKD), where entanglement enables fundamentally secure cryptographic protocols resistant to eavesdropping. We present an in-depth analysis of various QKD protocols, including BB84, E91, and decoy-state methods, assessing their security, efficiency, and practical feasibility. Recent experimental advancements in entanglement-based cryptography are examined, alongside real-world implementations and their technical challenges, such as photon loss, decoherence, and scalability in long-distance quantum communication networks. Additionally, we provide comparative insights into the efficiency of different QKD protocols using a bar chart, while figures and tables illustrate core quantum principles and experimental setups. By addressing both theoretical and practical aspects, this study contributes to a comprehensive understanding of quantum entanglement’s role in secure communication and highlights future directions for overcoming existing technological limitations.
Quantum cryptography represents a revolutionary paradigm shift in secure communication by leveraging the principles of quantum mechanics to guarantee unbreakable encryption. Unlike classical cryptographic methods dependent on computational hardness, quantum cryptography exploits quantum phenomena such as superposition and entanglement to provide provable security against eavesdropping. This paper explores fundamental quantum cryptographic protocols, their operational principles, and recent advances that enable practical deployment. We further discuss challenges, implementation issues, and the future scope of quantum key distribution (QKD) technologies in securing global communication infrastructures
The rapid advancement of quantum computing poses a significant threat to classical cryptographic systems that rely on the computational hardness of mathematical problems such as integer factorization and discrete logarithm problems. In this context, quantum cryptography has emerged as a promising paradigm for secure communication based on the fundamental principles of quantum mechanics rather than on computational assumptions. This paper presents a comprehensive review of quantum cryptography, with a particular focus on Quantum Key Distribution (QKD), the most mature application. The study discusses the theoretical foundations of quantum security, including superposition, entanglement, and the No-cloning theorem, which collectively enable eavesdropping detection and guarantee information-theoretic security. Furthermore, the review examines major QKD protocols, such as BB84 and E91, as well as their advanced variants designed to address practical vulnerabilities and enhance performance. Recent progress in real-world implementations, including fiber-optic networks, free-space communication, and satellite-based systems such as the Micius satellite, is also analyzed. In addition, the paper highlights critical challenges related to scalability, hardware limitations, and security loopholes arising from imperfect devices. Finally, emerging research directions, including hybrid cryptographic frameworks that integrate quantum and post-quantum approaches, are discussed to provide insights into the future of secure communication. This review aims to provide a structured, up-to-date understanding of quantum cryptography, bridging the gap between theoretical developments and practical implementations, and emphasizing its crucial role in shaping next-generation cybersecurity systems.
Quantum cryptography is based on quantum mechanics to guarantee secure communication.It allows two parties to produce a shared random bit string known only to them.These random bits can be used as a key to encrypt and decrypt messages.The most important and unique property of quantum cryptography is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key.It is based on fundamental aspects of quantum mechanics.By using quantum entanglement or quantum super positions and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping.Quantum cryptography is used to produce and distribute a key, not to transmit any message data.This key along with certain encryption algorithm, is used to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel.This paper concentrates on comparison between classical and quantum cryptography as well as survey on various quantum key distribution protocols used to generate and distribute the key among communicating parties.