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Q: Fachverband Quantenoptik und Photonik

Q 62: Poster – Quantum Information Technologies (joint session Q/QI)

Q 62.4: Poster

Donnerstag, 13. März 2025, 17:00–19:00, Tent

Device-independent quantum key distribution with atom-photon entanglement for an urban fiber link — •Jonas Meiers, Christian Haen, Max Bergerhoff, 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 device-independent implementation with a ⁴⁰Ca⁺-ion as quantum memory. The protocol requires four atomic bases and two photonic bases and allows us to create a quantum key with security verification via the Bell parameter. We employ polarization entanglement between a single trapped ⁴⁰Ca⁺ ion and an emitted photon at 854 nm, generated via the P_3/2 → D_5/2 transition [2]. The photon is frequency-converted to the telecom band, enabling its transmission over our 15-km-long urban fiber link across Saarbrücken [3]. The fiber link has been characterized and stabilized for the transmission of polarization-encoded qubits. The projected qubits are error-corrected via a cascade algorithm to create the secure key and enable secure communication between the two nodes.
[1] R. Schwonnek et al., Nat. Commun. 12, 2880 (2021)
[2] M. Bock et al., Nat. Commun. 9, 1998 (2018)
[3] S.Kucera et al., npj Quantum Inf. 10, 88 (2024)

Keywords: Quantum information; Quantum network; Fiber link; Quantum Memory