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arXiv · 2512.11625

Polarization Entanglement in Atomic Biphotons via OAM-to-Spin Mapping

Chang-Wei Lin·Yi-Ting Ma·Jiun-Shiuan Shiu·Yong-Fan Chen
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Abstract

We demonstrate polarization-entangled biphotons in a cold-atom double-$\Lambda$ system, overcoming atomic selection rules that suppress polarization correlations and favor orbital angular momentum (OAM) entanglement. Using spatial light modulators, we coherently map a selected two-dimensional OAM subspace onto the polarization basis and thereby open an otherwise inaccessible polarization channel. Quantum-state tomography confirms that the mapping preserves the biphoton coherence. The four polarization Bell states are generated with fidelities of $92\text{-}94\%$ with few-percent statistical uncertainties, and an average Clauser-Horne-Shimony-Holt parameter of $S=2.44$ verifies the survival of nonlocal correlations. To the best of our knowledge, this work presents the first demonstration of OAM-to-polarization entanglement transfer in a cold-atom spontaneous four-wave mixing platform and establishes a practical interface for integrating atomic OAM resources with polarization-based quantum communication networks.

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Chang-Wei Lin, Yi-Ting Ma, Jiun-Shiuan Shiu, Yong-Fan Chen. 2025-12-12. Polarization Entanglement in Atomic Biphotons via OAM-to-Spin Mapping. https://arxiv.org/abs/2512.11625

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