Mainz 2026 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 10: Quantum Technologies – Photon Detectors and Sources
Q 10.8: Talk
Monday, March 2, 2026, 18:45–19:00, P 5
Generation of polarization-entangled Bell states in monolithic photonic waveguides by leveraging intrinsic crystal properties — Trevor Vrckovnik1,2, Dennis Arslan1, Falk Eilenberger1,2, and •Sebastian Schmitt1,2 — 1Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Albert-Einstein-Str. 7, 07745 Jena, Germany — 2Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany
Advanced photonic quantum technologies-from quantum key distribution to quantum computing-require on-chip sources of entangled photons that are both efficient and scalable. This theoretical study demonstrates the generation of polarization-entangled Bell states in structurally simple waveguides by exploiting intrinsic nonlinear-crystal properties, eliminating the need for elaborate phase-matching schemes based on spatial modulation. We derive general criteria for the second-order susceptibility tensor that enable cross-polarized photon-pair generation via spontaneous parametric down-conversion in single-material waveguides and categorize all birefringent, non-centrosymmetric crystal classes accordingly. Using coupled-mode theory, we numerically analyze cuboid waveguides made from lithium niobate and barium titanate. Barium titanate consistently outperforms lithium niobate, offering higher nonlinear efficiency and high concurrence over a much broader spectral range. These findings outline a practical path toward efficient, fabrication-friendly, and scalable sources of polarization-entangled photons for integrated quantum photonic circuits.
Keywords: polarization-entangled Bell states; barium titanate waveguide; lithium niobate waveguide; spontaneous parametric down conversion; integrated quantum photonics