Practical high-dimensional quantum key distribution protocol over deployed multicore fiber

• Published in: Nature communications Vol. 15; no. 1; p. 1651
• Main Authors: Zahidy, Mujtaba, Ribezzo, Domenico, De Lazzari, Claudia, Vagniluca, Ilaria, Biagi, Nicola, Müller, Ronny, Occhipinti, Tommaso, Oxenløwe, Leif K., Galili, Michael, Hayashi, Tetsuya, Cassioli, Dajana, Mecozzi, Antonio, Antonelli, Cristian, Zavatta, Alessandro, Bacco, Davide
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23-02-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/483; 639/766/483/481; Coding; Communication; Cybersecurity; Data encryption; Digital data; Electric industries; Fiber technology; Humanities and Social Sciences; Hybrid systems; multidisciplinary; Optical fibers; Photonics; Principles; Protocol; Quantum cryptography; Quantum theory; Science; Science (multidisciplinary)
• DOI: 10.1038/s41467-024-45876-x
• EISSN: 2041-1723

Quantum key distribution (QKD) is a secure communication scheme for sharing symmetric cryptographic keys based on the laws of quantum physics, and is considered a key player in the realm of cyber-security. A critical challenge for QKD systems comes from the fact that the ever-increasing rates at which digital data are transmitted require more and more performing sources of quantum keys, primarily in terms of secret key generation rate. High-dimensional QKD based on path encoding has been proposed as a candidate approach to address this challenge. However, while proof-of-principle demonstrations based on lab experiments have been reported in the literature, demonstrations in realistic environments are still missing. Here we report the generation of secret keys in a 4-dimensional hybrid time-path-encoded QKD system over a 52-km deployed multicore fiber link forming by looping back two cores of a 26-km 4-core optical fiber. Our results indicate that robust high-dimensional QKD can be implemented in a realistic environment by combining standard telecom equipment with emerging multicore fiber technology.
High-dimensional QKD would in principle allow for several advantages over its bidimensional counterpart, but in-the-field demonstrations are missing. Here, the authors realise 4- dimensional hybrid time-path-encoded QKD using a 52-km deployed multicore fiber link.