Alain Aspect’s speech at the Nobel Prize banquet, 10 December 2022.

Your Majesties, Your Royal Highnesses, Excellencies, Dear Laureates, Ladies and gentlemen:

On behalf of Dr John Clauser, Prof Anton Zeilinger and myself, we wish to thank The Royal Swedish Academy of Sciences and the Nobel Foundation for the invaluable honour of this prize. That recognition should go first to the late John Stuart Bell, without whom we would not be here today.

“Do you have a permanent position?” These were the first words of John Bell, in 1975, when I finished describing the scheme of the experiment I was planning. He explained that working on a test of the inequalities he had found would be considered a waste of time, as John Clauser knows well. But when I told him that I had a tenured position, he encouraged me to pursue a project that would address the core of Einstein’s thinking.

Bell had demonstrated that one can settle experimentally a long-standing debate between Albert Einstein and Niels Bohr about the interpretation of the quantum formalism. The debate focused on a quantum situation described by Einstein, Podolsky and Rosen in 1935, where two particles are in a state that Schrödinger named “entangled” to emphasize the link between the particles even widely separated. It was, it appeared, merely a debate about how to interpret the results of a calculation on which there was no disagreement. But in 1964, John Bell discovered that adopting Einstein’s point of view about the nature of physical reality would lead to a result in contradiction with the quantum predictions, in some situations. A seemingly philosophical debate about the nature of physical reality could be settled by an experiment!  How could one not be amazed and attracted by such a discovery?

Beginning in 1972, the three of us successively developed realizations of such an experiment, with increasing sophistication. The conclusion is now clear:  Einstein’s view on physical reality cannot be upheld. Entanglement is confirmed in its strangest aspects. Nowadays entanglement is at the heart of a flourishing of quantum technologies, some based on experiments by Anton Zeilinger. We must thank Einstein, Bohr and Bell for pointing out that extraordinary property of the quantum world.

Copyright © The Nobel Foundation 2022