Full-field mapping of spatially varying polarization entanglement generated from spontaneous parametric down-conversion
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. We observe an entire class of near-maximally polarization-entangled states with an average concurrence of , which, together with a certified spatial dimensionality of 148, could potentially offer access to a 251-dimensional hyperentanglement. 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.
Cite
@article{arxiv.2502.03586,
title = {Full-field mapping of spatially varying polarization entanglement generated from spontaneous parametric down-conversion},
author = {Cheng Li and Girish Kulkarni and Isaac Soward and Yingwen Zhang and Jeremy Upham and Duncan England and Andrei Nomerotski and Ebrahim Karimi and Robert Boyd},
journal= {arXiv preprint arXiv:2502.03586},
year = {2026}
}