Bell’s inequality and the spooky actions at a distance

This article discusses the main aspects related to Bell’s inequality, both theoretical and experimental. A new derivation of Bell’s inequality is also presented, which stands out for its mathematical simplicity. The exposition is mainly intended for undergraduate physics students, and places special emphasis on clarifying the meaning and scope of Bell’s theorem in the context of the Einstein-Podolski-Rosen experiment.

Keywords:
Bell’s inequality; EPR experiment; quantum entanglement; Wigner-d’Espagnat inequality