[brianfitz]

TL;DR: There was a loophole found in an older thought experiment that indicated that at the quantum level, nothing is real until it is observed.

A discovery was recently made that found a way to add an unknown variable into the mix such that an expiriment where the future seems to affect the past was possibly explained away by a classical model.

However, a new experiment was proposed to show whether the new classical model actually was the explanation — and it turns out this classical “loophole” can not explain it.

So we’re now back to the beginning where it once again appears that nothing is real until observed at a quantum level which is also referred to as “anti-realism”.

[seppel]

> nothing is real until it is observed.

What do the terms "real" and "observed" mean in this sentence?

[Diggsey]

Pretty sure local hidden variable theories were ruled out as an explanation of quantum mechanics a long time ago. What's new here?

[21]

Wikipedia says that this is the conclusion of Wheeler's experiment:

> Any explanation of what goes on in a specific individual observation of one photon has to take into account the whole experimental apparatus of the complete quantum state consisting of both photons, and it can only make sense after all information concerning complementary variables has been recorded. Our results demonstrate that the viewpoint that the system photon behaves either definitely as a wave or definitely as a particle would require faster-than-light communication. Because this would be in strong tension with the special theory of relativity, we believe that such a viewpoint should be given up entirely.

[naasking]

Local hidden variables are only ruled out if you reject superdeterminism. At least one Nobel prize winning physicist is developing a superdeterministic theory of QM.

And of course, non-local classical theories like de Broglie-Bohm are just fine, once again.

[Ygg2]

They weren't. There was an error or oversight in the proof.