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Laser Physics Letters

Entanglement based six-state quantum cryptography protocol: exact proof of security

S. P. Kulik, S. N. Molotkov

Published Apr 25, 2023• 0 citations
Publisher

Abstract

Abstract A novel quantum key distribution (QKD) protocol is proposed, which uses six states of three states in two bases. The protocol provides a greater range of key distribution compared to known QKD protocols. The protocol has an accurate proof of secrecy based on fundamental entropy uncertainty relations, the use of which is possible with the entanglement version of the protocol. The implementation of the protocol does not require adjustment of the polarization state at the output of the communication line, since the receiving side does not use active polarization-sensitive elements—phase modulators, which virtually excludes active probing of the active elements of the system.

DOI
10.1088/1612-202x/accce5

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Abstract A novel quantum key distribution (QKD) protocol is proposed, which uses six states of three states in two bases. The protocol provides a greater range of key distribution compared to known QKD protocols. The protocol has an accurate proof of secrecy based on fundamental entropy uncertainty relations, the use of which is possible with the entanglement version of the protocol. The implementation of the protocol does not require adjustment of the polarization state at the output of the communication line, since the receiving side does not use active polarization-sensitive elements—phase modulators, which virtually excludes active probing of the active elements of the system.
In secure communication, quantum key distribution (QKD) based on coherent states is well known for its simple implementation, but it suffers from loss-dependent attacks, and generally underestimates the final secure key rate. To address this problem, the authors present a six-coherent-state phase-encoding QKD protocol based on non-phase-randomized coherent states, with which secret key rates and transmission distance can be significantly improved. The security of the protocol is determined using a recently developed security-proof technique based on semidefinite programming. These results point to this protocol as a promising candidate for high-speed, provably secure QKD.
Abstract Since the 80 s when it was first proposed, Quantum Key Distribution (QKD) elicited great interest in the field of cryptography as a unique procedure for key generation that could in principle guarantee unconditionally secure communication “by the laws of Physics”. In the last fifteen years commercial solutions have started appearing on the market, showing that practical implementations of the protocol were not only possible but also competitive in terms of security and achievable secret-key rate. In this work we describe a simulation of the historical QKD protocol E91 on the IBM Quantum platform, making use of the qubit formalism to represent the quantum states received by two communicating nodes. Having implemented also the post-processing steps for the error correction and the privacy amplification, this model can represent a simple stand-alone tool to study the performance not only of one-to-one communication but of more complex systems that rely on QKD for security, one above all QKD networks.
The security of quantum key distribution (QKD) is established by a security proof, and the security proof puts some assumptions on the devices consisting of a QKD system. Among such assumptions, security proofs of the six-state protocol assume the use of photon number resolving (PNR) detector, and as a result the bit error rate threshold for secure key generation for the six-state protocol is higher than that for the BB84 protocol. Unfortunately, however, this type of detector is demanding in terms of technological level compared to the standard threshold detector, and removing the necessity of such a detector enhances the feasibility of the implementation of the six-state protocol. Here, we develop the security proof for the six-state protocol and show that we can use the threshold detector for the six-state protocol. Importantly, the bit error rate threshold for the key generation for the six-state protocol (12.611%) remains almost the same as the one (12.619%) that is derived from the existing security proofs assuming the use of PNR detectors. This clearly demonstrates feasibility of the six-state protocol with practical devices.
Quantum entanglement, a fundamental quantum phenomenon, holds the potential for revolutionary information encoding techniques. This paper explores the utilization of quantum entanglement for secure data transmission and the development of a novel protocol, termed Quantum Key Distribution (QKD) based on entangled states, aiming to surpass traditional cryptographic methods. The core mechanism centers around establishing a secure key distribution protocol leveraging the unique properties of entanglement. This research investigates the potential of this approach, focusing on the practical implementation and security analysis of the quantum entanglement encoding process. We will outline the theoretical underpinnings, design considerations, and preliminary results demonstrating the feasibility of this new approach. This paper presents a comprehensive assessment of the potential benefits and challenges associated with this paradigm shift in information security.
Abstract All known single-pass fiber-based systems of quantum cryptography require a permanent adjustment of the polarization of states at the output of the quantum channel (QC). A fundamentally new implementation of the single-pass system of quantum cryptography is proposed, which does not require adjustment of the polarization at the output of the QC. Compensation for polarization distortions in the QC occurs automatically on the receiving side—the distortions are self-compensating. This result is achieved due to the fact that the receiving side of the system does not contain active polarization sensitive elements—phase modulators, polarization modulators, polarization controllers etc. The solution of the problem is provided by using a special protocol of quantum key distribution, in which non-orthogonality of states from different bases is achieved due to the time shift.