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arXiv:2306.04599

Experimental demonstration of scalable quantum key distribution over a thousand kilometers

Aziz Aliev, Vladlen Statiev, Ilja Zarubin, N. S. Kirsanov, Daniel Strizhak, Alexander Bezruchenko, Alexandra Osicheva, Alexandr Smirnov, Mikhail Yarovikov, Aleksei Kodukhov, Valeria A. Pastushenko, Markus Pflitsch, V. M. Vinokur

Published Aug 21, 2023• 6 citations
arXivHTMLPDF

Abstract

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.

DOI
10.21203/rs.3.rs-3259005/v1

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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.
Quantum cryptography revolutionizes secure information transfer, providing defense against both quantum and classical computational attacks. The primary challenge in extending the reach of quantum communication comes from the exponential decay of signals over long distances. We meet this challenge by experimentally realizing the Quantum-Protected Control-Based Key Distribution (QCKD) protocol, utilizing physical control over signal losses. By ensuring significant non-orthogonality of the leaked quantum states, this control severely constrains eavesdroppers' capacities. We demonstrate the performance and scale of our protocol by experiments over a 1707 km long fiber line. The scalability of the QCKD opens the route for globally secure quantum-resistant communication.
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.
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
Quantum key distribution (QKD) aims to generate secure private keys shared by two remote parties. With its security being protected by principles of quantum mechanics, some technology challenges remain towards practical application of QKD. The major one is the distance limit, which is caused by the fact that a quantum signal cannot be amplified while the channel loss is exponential with the distance for photon transmission in optical fiber. Here using the 3-intensity sending-or-not-sending protocol with the actively-odd-parity-pairing method, we demonstrate a fiber-based twin-field QKD over 1002 km. In our experiment, we developed a dual-band phase estimation and ultra-low noise superconducting nanowire single-photon detectors to suppress the system noise to around 0.02 Hz. The secure key rate is 9.53×10^{-12} per pulse through 1002 km fiber in the asymptotic regime, and 8.75×10^{-12} per pulse at 952 km considering the finite size effect. Our work constitutes a critical step towards the future large-scale quantum network.
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 advancements in hardware, standardization, and hybrid cryptographic strategies for widespread adoption.
Abstract Entanglement-based quantum key distribution (QKD) is an essential ingredient in quantum communication, owing to the property of source-independent security and the potential on constructing large-scale quantum communication networks. However, implementation of entanglement-based QKD over long-distance optical fiber links is still challenging, especially over deployed fibers. In this work, we report an experimental QKD using energy-time entangled photon pairs that transmit over optical fibers of 242 km (including a section of 19 km deployed fibers). The QKD is realized through the protocol of dispersive-optics QKD (DO-QKD) with high-dimensional encoding to utilize coincidence counts more efficiently. A reliable, high-accuracy time synchronization technology for long-distance entanglement-based QKD is developed based on the distribution of optical pulses in quantum channels. Our system operates continuously for more than 7 d without active polarization or phase calibration. We ultimately generate secure keys with secure key rates of 0.22 bps and 0.06 bps in the asymptotic and finite-size regimes, respectively. It shows that entanglement-based DO-QKD is reliable for long-distance realization in the field if its high requirement on time synchronization is satisfied.