Experimentally faking the violation of Bell's inequalities

Abstract

Entanglement witnesses such as Bell inequalities are frequently used to prove the non-classicality of a light source and its suitability for further tasks. By demonstrating Bell inequality violations using classical light in common experimental arrangements, we highlight why strict locality and efficiency conditions are not optional, particularly in security-related scenarios.

Added discussion of countermeasures, updated references. This version is published in Phys. Rev. Lett. 5 pages, 4 figures