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arXiv · 2502.03586

Full-field mapping of spatially varying polarization entanglement generated from spontaneous parametric down-conversion

Cheng Li·Girish Kulkarni·Isaac Soward·Yingwen Zhang·Jeremy Upham·Duncan England·Andrei Nomerotski·Ebrahim Karimi·Robert Boyd
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Abstract

Two-photon states generated from spontaneous parametric down-conversion (SPDC) can display entanglement in all degrees of freedom (DoFs) of light, including spatial, temporal, and polarization. The coupling between different DoFs of a two-photon state has been shown to display rich structures that enable novel and robust information processing schemes. While existing literature has studied these couplings by post-selecting the SPDC field, a comprehensive understanding of the inherent spatial-polarization coupling produced in the SPDC process is still lacking. This work produces a full spatial map of the polarization entanglement generated across the entire SPDC field, which contains an entire class of near-maximally polarization-entangled states with an average concurrence of 0.8303 +/- 0.0004. The spatial-polarization coupling manifests as radially or linearly varying polarization-entangled states, whose wavefunctions are dependent on the transverse momenta of the down-converted photons and the pump beam, respectively. Our study lays important groundwork for further exploiting the coupling between entanglement in different DoFs for future quantum technologies

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Cheng Li, Girish Kulkarni, Isaac Soward, Yingwen Zhang, Jeremy Upham, Duncan England, Andrei Nomerotski, Ebrahim Karimi, Robert Boyd. 2025-02-05. Full-field mapping of spatially varying polarization entanglement generated from spontaneous parametric down-conversion. https://doi.org/10.1103/l9vh-14nj

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