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arXiv:2301.10610 · Scientific Reports

Forty thousand kilometers under quantum protection

N. S. Kirsanov, Valeria A. Pastushenko, Aleksei Kodukhov, Mikhail Yarovikov, Asel Sagingalieva, Dmitry Anatolevich Kronberg, Markus Pflitsch, V. M. Vinokur

Published May 30, 2023• 14 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) is a revolutionary cryptography response to the rapidly growing cyberattacks threat posed by quantum computing. Yet, the roadblock limiting the vast expanse of secure quantum communication is the exponential decay of the transmitted quantum signal with the distance. Today's quantum cryptography is trying to solve this problem by focusing on quantum repeaters. However, efficient and secure quantum repetition at sufficient distances is still far beyond modern technology. Here, we shift the paradigm and build the long-distance security of the QKD upon the quantum foundations of the Second Law of Thermodynamics and end-to-end physical oversight over the transmitted optical quantum states. Our approach enables us to realize quantum states' repetition by optical amplifiers keeping states' wave properties and phase coherence. The unprecedented secure distance range attainable through our approach opens the door for the development of scalable quantum-resistant communication networks of the future.

DOI
10.1038/s41598-023-35579-6

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Quantum key distribution (QKD) is a revolutionary cryptography response to the rapidly growing cyberattacks threat posed by quantum computing. Yet, the roadblock limiting the vast expanse of secure quantum communication is the exponential decay of the transmitted quantum signal with the distance. Today's quantum cryptography is trying to solve this problem by focusing on quantum repeaters. However, efficient and secure quantum repetition at sufficient distances is still far beyond modern technology. Here, we shift the paradigm and build the long-distance security of the QKD upon the quantum foundations of the Second Law of Thermodynamics and end-to-end physical oversight over the transmitted optical quantum states. Our approach enables us to realize quantum states' repetition by optical amplifiers keeping states' wave properties and phase coherence. The unprecedented secure distance range attainable through our approach opens the door for the development of scalable quantum-resistant communication networks of the future.
Abstract Secure long distance communications protecting the transmitting of sensitive information vital for business and advanced technologies from being accessed by unauthorized individuals, is one of the major challenges of modern life. The existing means of transmitted data protection are vulnerable to upcoming quantum computer attacks. Yet, remarkably, the quantum mechanics that engendered a threat to secure communications offers a guaranteed protection against the malicious attacks allowing to develop novel quantum key distribution (QKD). The major problem of the long-distance transmission arises due to essential signal decay in optical channels occurring at distances about a hundred kilometers. We resolve this problem by an original Terra Quantum QKD (TQ-QKD) protocol using semiclassical pulses containing enough photons for random bit encoding and exploiting erbium amplifiers to retranslate photon pulses and, at the same time, ensuring that at the chosen pulse intensity only a few photons can go outside the channel even at distances of about a hundred meters.As a result, an eavesdropper is incapable to utilize the lost part of the signal. A central component of the TQ-QKD protocol is the end-to-end loss control of the fiber-optic communication line. Our control precision reduces the degree of the signal leak below the detectable level, depriving an eavesdropper any possibility to efficiently utilize the lost part of the signal. Our work experimentally demonstrates the implementation of the TQ-QKD protocol allowing for a fully secure quantum key distribution over 1079 kilometers. Further refining of the transmitting scheme's components will expand the secure transmission scale over the global distances.
Existing quantum cryptography is resistant against secrecy-breaking quantum computers but suffers fast decay of the signal at long distances. The various types of repeaters of propagating quantum states have been developed to meet the challenge, but the problem is far from being solved. We step in the breach and put forth long-distance high secrecy optical cryptography, creating the fast quantum key distribution over distances up to 40,000 kilometers. The key element of the proposed protocol is the physical control over the transmission line.
Long-distance communication data cannot be safely sent over the Internet without strong key distribution mechanisms and long-term, secure communication routes. In recent days, distributing a secret key across faraway entities connected by an optical fibre or open space has been the goal of quantum key distribution. The previous quantum method challenge in guaranteeing the integrity of qubits makes long-distance communication a challenging endeavour. With a growing number of cyber dangers, it is more important than ever to guarantee safe interaction. Quantum computers can easily crack traditional key exchange techniques, which create shared secret keys for protection. A quantum key distributionbased secure communication model (QKD-SCM) has been suggested for large-scale networks to rapidly ascertain the bare minimum of quantum repeaters needed to provide end-to-end connections among all end hosts. The suggested QKD-SCM evaluates the safety and efficiency of existing point-to-point QKD systems. The QKD-SCM with Quantum repeaters setup breaks the channel into quantum memory (QM), which is climbable and allows for long-distance quantum communication. The end of the channel is used to produce entangled qubits. Experiments show that QKD-SCM can succeed in making long-distance networks very secure with less communication delay.
Quantum entanglement has emerged as a transformative principle in modern physics, offering unprecedented potential for secure communication. This study explores entanglement-driven architectures designed to enable ultra-secure communication networks resistant to classical and quantum-based cyber threats. It examines the theoretical foundations of quantum entanglement and its application in quantum key distribution (QKD), teleportation protocols, and network scalability. The research evaluates existing communication models and identifies limitations in terms of noise interference, transmission distance, and infrastructure complexity. Through a comparative analysis of classical encryption and quantum-based security mechanisms, the study highlights the superior resilience of entanglement-enabled systems against eavesdropping and data breaches. Furthermore, it investigates emerging technologies such as quantum repeaters and satellite-based quantum communication to address long-distance transmission challenges. The findings suggest that while entanglement-driven architectures hold significant promise, practical implementation requires advancements in hardware stability, error correction, and cost efficiency. This study contributes to the growing field of quantum communication by providing insights into scalable, secure network design and identifying future research directions necessary for real-world deployment.
The increasing reliance on optical communication networks for high-speed data transmission has amplified concerns regarding secure information exchange in the era of quantum computing. Classical cryptographic protocols such as RSA and ECC, though widely deployed, are vulnerable to attacks from large-scale quantum computers executing Shor’s algorithm. Quantum Key Distribution (QKD) has emerged as a revolutionary cryptographic paradigm that leverages the principles of quantum mechanics to enable theoretically unbreakable key exchange. This paper investigates the integration of QKD into optical communication networks, focusing on protocol design, implementation challenges, and potential scalability. Through scenario-based evaluation, the study highlights the trade-offs between quantum security and practical deployment constraints such as channel loss, photon detector efficiency, and key generation rates. Results from simulated models demonstrate that while QKD can achieve provable security in metropolitan-area networks, long-distance transmission requires advanced techniques such as quantum repeaters and trusted nodes. This work concludes that QKD offers a promising pathway toward quantum-safe communication but necessitates
Optical telecommunication is at the heart of today's internet and is currently enabled by the transmission of intense optical signals between remote locations. As we look to the future of telecommunication, quantum mechanics promise new ways to be able to transmit and process that information. Demonstrations of quantum key distribution and quantum teleportation using multiphoton states have been performed, but only over ranges limited to a few hundred kilometers. To go beyond this, we need repeaters that are compatible with these quantum multiphoton continuous-variable pulses. Here we present a design for continuous-variable quantum repeaters that can distribute entangled and pure two-mode squeezed states over arbitrarily long distances with a success probability that scales only polynomially with distance. The proposed quantum repeater is composed from several basic known building blocks such as non-Gaussian operations for entanglement distillation and an iterative Gaussification protocol (for retaining the Gaussian character of the final state), but complemented with a heralded non-Gaussian entanglement swapping protocol, which allows us to avoid extensive iterations of quantum Gaussification. We characterize the performance of this scheme in terms of key rates for quantum key distribution and show a secure key can be generated over thousands of kilometers.