Physicists Prove Quantum Weirdness in New Light Experiment
Researchers have demonstrated that certain quantum light-splitting processes violate the laws of classical physics, but only when measurements are controlled by switching the experiment on and off—not just adjusting settings. The finding validates a recent high-profile experiment and opens a new pathway for quantum technologies that exploit counterintuitive physics.
Originaltitel: Unquestionable Bell Theorem for Interwoven Frustrated Downconversion Processes
<p>Interwoven frustrated parametric down-conversion (PDC) processes produce interference effects based on Letter we show Bell nonclassicality of the processes: a proper violation of the Clauser-Horne inequality when the local measurements are controlled by on-off switching of the final local PDC processes. Such a nonstandard approach is needed because if only the local phase shifts are used for the measurement settings, as done in the experiment reported in Wang et al. [Violation of Bell inequality with unentangled photons, Sci. Adv. 11, eadr1794 (2025)], there exists a local realistic model of the interference, which we present in this Letter. Nevertheless, the reported destructive interference is deep enough to violate the inequality when using on-off switching, so our result establishes a firm footing for nonclassicality of the new interferometry, in both theory and experiment. The on-off approach to Bell analysis of path-identity-based interference forms a new platform for seeking new highly counterintuitive quantum phenomena.</p>