Jean Bricmont wrote on facebook a more detailed critique of the Nobel Committee text. Here I copy-paste the Bricmont's writing:
For my physics colleagues.
Like most people interested in foundations of quantum mechanics, I am very happy that a well deserved Nobel prize is awarded to three outstanding experimentalists interested in those foundations. However, I would like to make a few comments on the Press release on the Nobel Prize in Physics (https://www.nobelprize.org/.../physics/2022/press-release/):
Press release: One key factor in this development is how quantum mechanics allows two or more particles to exist in what is called an entangled state. What happens to one of the particles in an entangled pair determines what happens to the other particle, even if they are far apart.
Comment: That is correct. To be more precise, whenever some experiment is performed on one particle of the pair being in an entangled state, knowing the result of that experiment immediately foretells what the result of a similar experiment done on the other particle will be. And that is true no matter how far apart the particles are.
Press release: For a long time, the question was whether the correlation was because the particles in an entangled pair contained hidden variables, instructions that tell them which result they should give in an experiment.
Comment: this is correct but incomplete. That question was raised in 1935 paper by Einstein, Podolsky and Rosen in a widely misunderstood paper but in a different form: how do we explain those perfect corrections between results of experiments made on both particles, even when they are far apart from each other? There seems to be only two possibilities: either performing an experiment on one particle affects instantaneously the behavior of the other particle or both particles contain instructions that tell them which result they should give in those experiments.
But the first possibility means that there exist instantaneous actions at a distance in Nature, something that was inconceivable for Einstein, Podolsky and Rosen (and probably everybody else at that time). So, Einstein, Podolsky and Rosen thought that they had proven that particles do contain those instructions. Since those instructions are not part of the standard quantum mechanical formalism, they thought that they had proven that quantum mechanics is incomplete, which means that individual quantum system are characterized not only by their wave function or quantum state but also by those instructions, also called hidden variables.
Press release: In the 1960s, John Stewart Bell developed the mathematical inequality that is named after him. This states that if there are hidden variables, the correlation between the results of a large number of measurements will never exceed a certain value. However, quantum mechanics predicts that a certain type of experiment will violate Bell’s inequality, thus resulting in a stronger correlation than would otherwise be possible.
Comment: that is correct, but, if we remember the previous comment, it means that the only explanation for the perfect correlations between results of experiments made on both particles, even when they are far apart from each other, is that doing an experiment on one particle immediately affects the behavior of the other particle, i.e. that these « inconceivable » actions at a distance do exist in Nature.
Press release: John Clauser developed John Bell’s ideas, leading to a practical experiment. When he took the measurements, they supported quantum mechanics by clearly violating a Bell inequality. This means that quantum mechanics cannot be replaced by a theory that uses hidden variables.
Comment: That is rather wrong: the logic of the above remarks is that, if a Bell inequality is violated, then actions at a distance do exist in Nature. And concerning "hidden variables », it depends what one means: if, by that, one means the instructions whose existence Einstein, Podolsky and Rosen thought they had demonstrated, then indeed these variables do not exist. But the more standard meaning of that expression refers to any variables that characterize an individual quantum system on top of its wave function or quantum state.
And there exists a theory, the de Broglie-Bohm one, that does introduce such hidden variables, actually the most obvious ones, the particles’ positions. One should emphasize that the existence of those variables is not refuted by Bell’s arguments (or any other argument) and it would be very strange indeed if they were refuted by them, since Bell defended that theory almost through his entire life.
So, here is a paradox: Bell is credited for having refuted hidden variable theories, while he constantly defended and explained such a theory. Was he crazy? But then, why so much admiration for him?
It would be enough to read Bell’s collection of articles « Speakable and unspeakable in quantum mechanics » to notice his defense of the de Broglie-Bohm theory and his reasons for doing so. Unfortunately, very few physicists do that and, it seems, not even the members of the Nobel Committee.
