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HL: Fachverband Halbleiterphysik
HL 47: Focus Session: Quantum Technologies in Deployed Systems II
HL 47.4: Hauptvortrag
Donnerstag, 20. März 2025, 11:15–11:45, H17
Quantum communication protocols over a 14-km urban fiber link — •Jürgen Eschner — Universität des Saarlandes, Experimentalphysik, 66123 Saarbrücken, Germany
Quantum communication over urban telecom fibers poses challenges such as environmentally induced polarization fluctuations and lossy splices. We report on the characterization and operation of a 14-km long fiber link across Saarbrücken for quantum communication. The dark fiber has underground and overground sections and ∼ 9 dB attenuation. We stabilize its polarization with > 99% process fidelity up to 60 s. For implementing quantum communication protocols we employ a 40Ca+ single-ion quantum memory, an ion-resonant entangled photon-pair source, and quantum frequency conversion.
We distribute photonic entanglement without significant fidelity degradation. Using heralded absorption of one photon of the entangled pair, we also demonstrate atom-to-photon quantum state teleportation over the fiber link with ∼ 84% average fidelity [1].
In a laboratory experiment we also realize a quantum repeater cell based on two 40Ca+ ions that are asynchronously entangled with their emitted photons. By entanglement swapping via a Mølmer-Sørensen quantum gate on the ions, which are located in the same trap, we generate photon-photon entanglement with ∼ 76% average fidelity [2].
[1] S. Kucera et al., npj Quantum Information 10, 88 (2024)
[2] M. Bergerhoff et al., Phys. Rev. A 110, 032603 (2024)
Keywords: Quantum network; Quantum teleportation; Single-ion quantum memory; Entanglement distribution