Mainz 2026 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 29: Poster – Quantum Technologies I
Q 29.4: Poster
Tuesday, March 3, 2026, 17:00–19:00, Philo 2. OG
Polarization-entanglement distribution over a 28 km urban fiber link at telecom wavelength — •Akriti Raj1, Tobias Bauer1, Christian Haen1, David Lindler1, Quankui Yang2, Thorsten Passow2, Marko Härtelt2, Jürgen Eschner1, and Christoph Becher1 — 1Universität des Saarlandes, FR Physik, Campus E2.6, 66123 Saarbrücken — 2Fraunhofer-Institut für Angewandte Festkörperphysik IAF, Tullastr. 72, 79108 Freiburg
Entangled photon pair sources are essential resources for quantum technological applications. AlGaAs Bragg reflection waveguides are promising platform for such sources due to their high nonlinear coefficient, room temperature operation, and non-birefringent nature [1]. By using a type-II SPDC process, the down-converted photons are orthogonally polarized, and the generated photon pairs are inherently polarization entangled. Here, we present the generation and distribution of polarization-entangled photons over a 28 km dark fiber link [2]. The link consists of commercial fiber, deployed both underground and overhead, includes several patching points, resulting in a transmission loss of ≈ 19 dB. The source produces a state with 95.7 % fidelity and 92.4 % purity w.r.t. the |ψ+⟩ Bell state. After transmission over the actively stabilized [2] fiber link, the fidelity reduces to 87.9 % due to residual uncompensated polarization rotation whereas the purity remains unchanged (92 %). In summary, we demonstrate a room-temperature entangled photon pair source at telecom wavelength, suitable for real world quantum applications.
[1] F. Appas et al., J. Light. Technol. 40 (2022).
[2] S. Kucera et al., npj Quantum Inf. 10, 88 (2024).
Keywords: SPDC, Polarisation entanglement, AlGaAs waveguide