Freiburg 2024 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 38: Poster IV

Q 38.21: Poster

Mittwoch, 13. März 2024, 17:00–19:00, KG I Foyer

QKD with atom photon entanglement over an urban fiber link — •Jonas Meiers, Christian Haen, Max Bergerhoff, Stephan Kucera, and Jürgen Eschner — Universität des Saarlandes, Experimentalphysik, 66123 Saarbrücken

Quantum cryptographic protocols offer physical security through no-cloning or entanglement. Following the entanglement-based quantum key distribution protocol of [1], we present our implementation of atom-photon entanglement-based quantum key distribution over a telecom fiber in a metropolitan network. The protocol requires four atomic bases as well as two photonic bases and allows us to create a quantum key with security verification via the Bell parameter. We employ the polarization entanglement between a single trapped ⁴⁰Ca⁺-ion and an emitted photon at 854 nm according to [2], generated via the P_3/2→ D_5/2 transition. The photon is frequency-converted into the telecom band and transmitted via a 15-km long urban dark fiber across Saarbrücken. The fiber has been characterized and stabilized for the transmission of polarization-encoded qubits. Following the implementation we discuss how well the experimental data agree with the predictions from the theoretical protocol.
[1] R. Schwonnek et al., Nat. Commun. 12, 2880 (2021)
[2] M. Bock et al., Nat. Commun. 9, 1998 (2018)

Keywords: Quantum Key Distribution; Trapped-Ion; Atom-photon entanglemet; Cavity ion trap; Urban Fiber