Forty thousand kilometers under quantum protection

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.

Boosting Quantum Key Distribution via the End-to-End Loss Control

“…Building on Quantum Thermodynamics considerations, see Ref. [10], we argue that these natural losses cannot be effectively harvested by Eve. We carry out an illustrative analysis, the results of which show that efficient eavesdropping of natural losses would require the length of the collection apparatus that is impossible to practically realize at the present level of technology.…”

“…The line tomography as a constituent part of the key distribution process was originally proposed and thoroughly discussed in Ref. [10]. In this section, we briefly outline its basis and discuss its inalienable components.…”

“…Thus, global actions by Eve, such as substituting the line with a lossless channel or completely blocking certain signals, can be readily detected due to their significant impact on the line tomogram. We discuss this issue in detail in [10,16]. Consequently, these drastic Eve's actions would not provide an efficient method to interfere, since in case of these actions, the key generation will be immediately terminated by the legitimate users.…”

“…Thus, by complementing quantum mechanical restriction imposed on a potential eavesdropper with realistic restrictions stemming from the development of technology, we narrow the class of attacks that have to be considered down to attacks utilizing deliberate local interventions. Moreover, relying on the end-to-end loss control method proposed in [10], legitimate users can detect these local intrusions. Remarkably, we find that our approach enables legitimate users to employ higher signal intensities and radically improves key distribution rates.…”

Entanglement Classification for Three-qubit Pure Quantum System using Special Linear Group under the SLOCC Protocol

“…To put it simply, an object's properties between two or more objects are dependent to each other. Over the years, quantum entanglement has sparked a massive interest of research in numerous fields namely quantum computing, quantum cryptography and quantum teleportation [5][6][7][8][9][10][11][12][13][14][15].…”