Year: 2026
Type: article
Abstract: Bell inequality tests based on high-dimensional entanglement usually require measurements that can resolve multiple possible outcomes. However, the implementation of high-dimensional multioutcome measurements is often only emulated via a collection of "click or no-click" measurements. This reduction of multioutcome measurements to binary-outcome measurements opens a loophole in high-dimensional tests Bell inequalities that can be exploited by local hidden variable models [Tavakoli et al., Phys. Rev. A 111, 042433 (2025)PLRAAN2469-992610.1103/PhysRevA.111.042433]. Here, we close this loophole by using four-dimensional photonic path-mode entanglement and multioutcome detection. We test both the well-known Collins-Gisin-Linden-Massar-Popescu inequality and a related Bell inequality tailored for maximally entangled states in high dimension. We observe violations that are large enough to also rule out any quantum model based on entanglement of lower dimension, thereby demonstrating genuinely high-dimensional nonlocality free of the binarization loophole.
Source: Physical Review Letters
DOI: 10.1103/ydch-vgmy
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Stiftelsen för Strategisk Forskning, National Natural Science Foundation of China, Knut och Alice Wallenbergs Stiftelse, Vetenskapsrådet, Major Scientific and Technological Special Project of Guizhou Province, Natural Science Foundation of Anhui Province, Fundamental Research Funds for the Central Universities, Wallenberg Center for Quantum Technology, Chalmers University of Technology
OpenAlex ID: W7160049797