Nonlocal Talbot effect in the orbital angular momentum domain with entangled photons.

The Talbot effect, a wave-optical self-imaging phenomenon originally observed in real-space, has developed into a powerful framework for programmable modal transformations across diverse physical platforms. Here, we report the experimental demonstration of nonlocal Talbot transformations within a high-dimensional, orbital angular momentum (OAM) entangled two-photon system. By exploiting the intrinsic nonlocal correlations generated through spontaneous parametric down-conversion, we show that applying an azimuthal Talbot phase on one photon of an entangled pair is sufficient to coherently reshape the OAM modal distribution of its spatially separated partner, without any direct local operation on the latter. As a proof of principle, we further demonstrate the inverse Talbot transformation within the same platform by incorporating the required quadratic phase during the state-preparation stage. These results extend Talbot physics from local mode manipulation to entanglement-assisted nonlocal transformations in a high-dimensional discrete basis. The demonstrated platform opens versatile routes toward conditional remote OAM-mode conversion, structured entangled-state engineering, and high-dimensional quantum information processing.