We still don’t know if the wavefunction is physically real

Nature has a piece claiming that a newly-published paper shows that the quantum mechanical wavefunction is physically real, as opposed to merely encoding information about our knowledge of the state of a system. As I mentioned back in the fall, I can’t see how the published result shows anything like this.

The paper shows that a certain class of hidden-variable theories would lead to predictions that differ from standard quantum mechanics, and hence that experiments can in principle tell the difference between these theories and quantum mechanics. But that doesn’t show that the wavefunction is real, unless you believe that this particular class of hidden-variable theories is the only thing that the wavefunction-isn’t-real camp could possibly believe. There’s certainly no evidence that this is the case.

Personally, I’m not sure the question of whether the wavefunction is “physically real” is meaningful. I am pretty sure that, even if it is, this paper doesn’t resolve it.