Extraordinary Claims Require Extraordinary Evidence: Closing Loopholes in Bell’s Inequality Expts

A colloquium delivered by Professor Gregor Weihs from the University of Innsbruck, Austria.

Abstract of the talk:
John S. Bell gave to us what many consider one of the most important theorems in physics by proving that quantum mechanics is incompatible with a local realistic world view. He thus challenged the widely prevailing paradigm that the probabilistic predictions of quantum theory are a mere way of accounting for the statistics of underlying real events. To this day there are scientists – albeit a shrinking number – who are unable to accept the consequences of this discovery and are still seeking flaws in the argument or the series of experiments that went to look whether nature does actually behave as predicted by quantum theory and thus violate Bell’s inequality.
Whenever claims are put forward that threaten to shatter our former beliefs, theoreticians and experimenters must produce watertight chains of evidence to prove the new truth. In the 50-year long history of experiments on Bell’s inequality a number of loopholes in the correspondence between the ideal theory and the necessarily imperfect experiments caused researchers to come up with better and better schemes that closed one loophole after the other.
In my presentation I will give an account of the historical situation and discuss our own contributions to the closure of the locality loophole by fast random switching in an experimental setting with remote measurement stations. This experiment served as the blueprint for several follow-up experiments that were eventually able to close all the loopholes at the same time using the latest source and detection technologies.