The PBR theorem is another theorem of quantum mechanics, which could go alongside Bell’s Theorem and the Kochen-Specker Theorem. I wrote this explanation in 2011, before the paper was officially published in Nature. Since then, it’s been recognized as a moderately important theorem, and it has been named after its three authors (Pusey, Barrett, and Rudolph). But at the time I didn’t really know whether it would become important.

There’s a new paper on arxiv called “The quantum state cannot be interpreted statistically “. It has a theorem which proves that, given a few basic assumptions, the quantum state (ie the wavefunction) must be real, rather than a merely statistical object. Nature has an article which mostly just harps on how “seismic” the paper is.

Nature (correction: the article’s author, not Nature itself) compares its importance to Bell’s Theorem, which is a very important result indeed from 1964. Bell’s theorem proved that if there were “hidden variables” underneath the quantum state, then entangled particles must be communicating with each other faster than light. I’ve explained Bell’s theorem in the past.

According to quantum mechanics, a vacuum isn’t empty at all. It’s actually filled with quantum energy and particles that blink in and out of existence for a fleeting moment — strange signals that are known as quantum fluctuations.

For decades, there had only ever been indirect evidence of these fluctuations, but back in 2015, researchers claimed to have detected the theoretical fluctuations directly. And now the same team says they’ve gone a step further, having manipulated the vacuum itself, and detecting the changes in these strange signals in the void.

We’re entering the territory of high-level physics here, but what’s really important in this experiment is that, if these results are confirmed, the researchers might have just unlocked a way to observe, probe, and test the quantum realm without interfering with it.