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Q: Fachverband Quantenoptik und Photonik

Q 31: Quantum Communication IV

Q 31.1: Talk

Wednesday, March 13, 2024, 11:00–11:15, HS 3219

Free-Space Quantum Key Distribution at Daylight using the Sodium D₂ Line — •Ilija Funk, Yagana Syed, and Ilja Gerhardt — Leibniz University Hannover, light & matter group, Appelstrasse 2, 30167 Hannover

Quantum key distribution is a promising pathway to secure communication in the future. Currently, quantum communication channels usually are realized through a fiber or a free-space network. While the latter offers much longer transmission distances of hundreds of kilometers compared to fiber links, it suffers from reduced transmission rates during daytime due to increased detection noise from sunlight. To circumvent this problem, we propose a free-space link based on entangled photon pairs with a wavelength of 589 nm. This wavelength coincides with the sodium D₂ line which is one of the most prominent Fraunhofer lines. Hence during daytime, the reduced amount of sunlight at this wavelength should allow for an improved transmission rate. Our research project includes the creation of entangled photon pairs at 589 nm, setting up a free-space link over several kilometers using telescopes, and demonstrating quantum key distribution using the BBM92 protocol. We report on our latest progress.

Keywords: qkd; fraunhofer line; free-space; sunlight; daylight