How ‘spooky’ is quantum physics? The answer could be incalculable

Davide Castelvecchi in Nature:

Albert Einstein famously said that quantum mechanics should allow two objects to affect each other’s behaviour instantly across vast distances, something he dubbed “spooky action at a distance”1. Decades after his death, experiments confirmed this. But, to this day, it remains unclear exactly how much coordination nature allows between distant objects. Now, five researchers say they have solved a theoretical problem that shows that the answer is, in principle, unknowable.

The team’s proof, presented in a 165-page paper, was posted on on the arXiv preprint repository on 14 January2, and has yet to be peer reviewed. If it holds up, it will solve in one fell swoop a number of related problems in pure mathematics, quantum mechanics and a branch of computer science known as complexity theory. In particular, it will answer a mathematical question that has been unsolved for more than 40 years.

More here.