Colloquium: "Quantum non-locality and beyond"

Professor Sandu Popescu is a 2022/2023 IAS Distinguished Scholar of the Mortimer and Raymond Sackler Institute of Advanced Studies.

Abstract: 

Long considered to be a fringe aspect of quantum mechanics, non-locality is now understood to be one of the main aspects of nature – and the experimental proof of its existence via the so-called Bell inequality violations has been rewarded with the Nobel Prize 2022. In my talk I will explain, in elementary terms, what non-locality is. I will then focus on an even more exciting issue. That nonlocality can exist at all, given the constraints imposed by relativistic causality, is an extraordinary fact. Surprisingly, it was found that even stronger nonlocal correlations are possible in principle, without contradicting relativity. Whether or not such correlations exist in nature is an open experimental question. If they exist, quantum mechanics is wrong and has to be replaced. If they do not exist - why not? What is the fundamental physical principle that forbids them? Could quantum mechanics be derived not from the study of spectra of atoms and such but from taking the existence of non-locality and these new principles as basic axioms? Here, I will describe some of the recent directions in the intensive effort to answer this question.