Practical high-dimensional quantum key distribution protocol over deployed multicore fiber
Mujtaba Zahidy, Domenico Ribezzo, Claudia De Lazzari, Ilaria Vagniluca, Nicola Biagi, Ronny Müller, Tommaso Occhipinti, Leif Katsuo Oxenløwe, Michael Galili, Tetsuya Hayashi, Dajana Cassioli, Antonio Mecozzi, Cristian Antonelli, Alessandro Zavatta, Davide Bacco
Abstract
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.