Confronting a New Fact of Nature: Bell’s Theorem and the Aspect and Gisin Experiments

Abstract

The origins of the thought experiment that became the basis for the actual experiments testing the predictions of Bell’s theorem can be traced to central issues in a debate between Bohr and Einstein. This debate began at the fifth Solvay Congress in 1927 and continued intermittently until Einstein’s death in 1955. The argument took the form of thought experiments in which Einstein would try to demonstrate that it was theoretically possible to measure, or at least determine precise values for, two complementary constructs in quantum physics, like position and momentum, simultaneously. Bohr would then respond with a careful analysis of the conditions and results in Einstein’s thought experiments and demonstrate that there were fundamental ambiguities he had failed to resolve. Although both men would have despised the use of the term, Bohr was the “winner” on all counts. Eventually, the dialog revolved around the issue of “realism,” and it is this issue that Einstein felt would decide the correctness of quantum theory.

We may safely say that nonseparability is now one of the most certain general concepts in physics.

Bernard d’Espagnat