Donnie Darko

Multiple realities aren’t just science fiction anymore

Contributed by
Mar 22, 2019

Existing in more than one reality like Donnie Darko is something that has been imagined by sci-fi almost as long as the genre has existed, but always impossible in real life (on a subatomic level or otherwise) until now.

What could once only be explored by a thought experiment has finally been proven by an international team of researchers. Said thought experiment, the brainchild of Nobel Prize-winning physicist Eugene Wigner, gave a scenario in which two observers looking at the same photon (light particle) would see it in two different states—and neither person would be hallucinating. Horizontal or vertical? Right answer either way.

"You can verify both of them," study co-author Martin Ringbauer, a postdoctoral researcher and co-author of a recent groundbreaking study, told LiveScience.

Quantum mechanics is a strange area to venture into. Once you get to that level, you’re dealing with infinitesimal particles that can bend the laws of physics. It was assumed by Wigner that a before a photon is measured exists in a superposition of two potential states—its polarization (the axis it spins on) can appear to be horizontal or vertical.

Enter Wigner’s friend. This is an imaginary friend, but you get the point.

Bring someone into the lab to measure a photon, the photon would end up in a definite horizontal or vertical polarization. This is basically the point of no return. But. The reality for a friend of that observer’s standing right outside the closed door of that lab diverges, because for them, that photon still exists in a superposition. Quantum mechanics says both of these realities are … reality.

"Theoretical advances were needed to formulate the problem in a way that is testable. Then the experimental side needed developments on the control of quantum systems to implement something like that," Ringbauer explained.

NASA image of stars

Innumberable stars mean innumerable photons in space. Credit: NASA

The real-life experiment leveled up Wigner’s thought experiment by doubling everything. Dual pairs of entangled photons were introduced to two “labs” designed specifically for the experiment. Because the fates of the photons are linked through entanglement, you already know the fate of one if you know the fate of the other. Everything up to this point is real. Only the four “friends” introduced to the experiment were non-corporeal.

“Inside” the closed “labs” were two of the “friends,” who measured one photon in each entangled pair and broke the entanglement, collapsing the superposition and ending up with an observation of either a horizontal or a vertical state of polarization. The results from the first photons in those pairs were recorded in quantum memory, meaning they were copied into the polarization of the second photons.

The other two “friends,” who were outside the labs, were presented with a choice before conducting observations. They could either measure their friends’ results, which were locked in quantum memory, or conduct what is known as an interference experiment. If the photons behaved like waves and still existed in that superposition—still holding those two possibilities—these observers would see the ups and downs of these light waves either add up or cancel each other out in a pattern of light and dark fringes. Different patterns would appear depending on whether the particles had or hadn’t settled into a fixed state.

Guess what. The experiment came out exactly as Wigner would have predicted.

Just one thing. If the measurements aren’t absolutes, that could bend even the weird rules of quantum mechanics. Let’s see sci-fi handle that.

(via LiveScience)

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