Time-bin encoding quantum key distribution in free-space horizontal links during nighttime and daytime

Fuente: arXiv
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Main Authors: Cocchi, Sebastiano, Ribezzo, Domenico, Guarda, Giulia, Centorrino, Pietro, Occhipinti, Tommaso, Zavatta, Alessandro, Bacco, Davide
Format: Preprint
Published: 2025
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author Cocchi, Sebastiano
Ribezzo, Domenico
Guarda, Giulia
Centorrino, Pietro
Occhipinti, Tommaso
Zavatta, Alessandro
Bacco, Davide
author_facet Cocchi, Sebastiano
Ribezzo, Domenico
Guarda, Giulia
Centorrino, Pietro
Occhipinti, Tommaso
Zavatta, Alessandro
Bacco, Davide
contents Free-space quantum key distribution (QKD) represents a groundbreaking advancement in secure communication, enabling secure key exchange over vast distances and offering robust encryption for the future quantum internet. However, the compatibility between fiber and free-space infrastructures continues to pose challenges for QKD protocols. Indeed, free-space and fiber-based networks commonly use different wavelengths and qubits encoding schemes. On the one hand, free-space QKD typically exploits visible light for its beneficial beam divergence compared to longer wavelengths, and polarization encoding for its robustness against turbulence. On the other hand, fiber-based QKD employs infrared light, particularly the C-band, because it shows the minimum losses with silica fibers, and time-bin encoding, due to polarization instability in optical fibers. In our study, we demonstrate the viability of a time-bin encoded QKD protocol operating in the C-band through horizontal turbulent free-space channels. We test the setup into a 50 m and a 500 m long links, achieving an average secure key rate of, respectively, 793 kbps and 40 kbps over several hours of measurements. The results encourage further exploration of the interoperability between free-space and fiber-based infrastructures, opening new possibilities for connecting terminal users with satellites in hybrid infrastructures.
format Preprint
id arxiv_https___arxiv_org_abs_2501_08891
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Time-bin encoding quantum key distribution in free-space horizontal links during nighttime and daytime
Cocchi, Sebastiano
Ribezzo, Domenico
Guarda, Giulia
Centorrino, Pietro
Occhipinti, Tommaso
Zavatta, Alessandro
Bacco, Davide
Quantum Physics
Free-space quantum key distribution (QKD) represents a groundbreaking advancement in secure communication, enabling secure key exchange over vast distances and offering robust encryption for the future quantum internet. However, the compatibility between fiber and free-space infrastructures continues to pose challenges for QKD protocols. Indeed, free-space and fiber-based networks commonly use different wavelengths and qubits encoding schemes. On the one hand, free-space QKD typically exploits visible light for its beneficial beam divergence compared to longer wavelengths, and polarization encoding for its robustness against turbulence. On the other hand, fiber-based QKD employs infrared light, particularly the C-band, because it shows the minimum losses with silica fibers, and time-bin encoding, due to polarization instability in optical fibers. In our study, we demonstrate the viability of a time-bin encoded QKD protocol operating in the C-band through horizontal turbulent free-space channels. We test the setup into a 50 m and a 500 m long links, achieving an average secure key rate of, respectively, 793 kbps and 40 kbps over several hours of measurements. The results encourage further exploration of the interoperability between free-space and fiber-based infrastructures, opening new possibilities for connecting terminal users with satellites in hybrid infrastructures.
title Time-bin encoding quantum key distribution in free-space horizontal links during nighttime and daytime
topic Quantum Physics
url https://arxiv.org/abs/2501.08891