Bell’s Theorem and Its Experiments

Abstract

Quantum mechanics makes surprising predictions that defy our classical understanding of the world. Experiments done on entangled particles—particles with linked properties—prove that actions on one particle can affect the other one no matter the distance. In response, physicists came up with local hidden variable theories in an attempt to understand this quantum phenomena through a classical lens. John Bell formulated a way to test whether nature is dictated by local hidden variable theories or quantum mechanics, and since then it has been the goal of numerous physicists to experimentally test the theorem and improve upon the results. This paper describes the history of these experiments, their pros and cons, their advancements, and the potential applications that they will enable.