Over the years, quantum physics has fed us a constant drip of mind-bending implications for the nature of reality. Of course, a lot of those mind-bending implications have been grossly misinterpreted, blended up, and turned into nonsense and predatory self-help books. It’s a funny field of research because while it is grossly misinterpreted, often and loudly, it also does challenge our assumptions about reality itself. Many of these challenges haven’t made it past the thought experiment phase. Recently, however, a real-life test of a famous quantum physics thought experiment was performed, and, according to the MIT Technology Review, the results are as weird as you could hope for.
The thought experiment is called the “Wigner’s Friend” experiment. Developed by Nobel Prize-winning physicist Eugene Wigner in 1961, the Wigner’s Friend thought experiment deals with quantum weirdness of light and the effect of the observer on quantum superposition. The thought experiment asks if two people can observe one event, see different things, and both be correct, essentially creating two different realities that are forced to coexist.
It works like this: A single polarized photon can have either a vertical polarization or a horizontal polarization. Until the measurement of it’s polarization happens, according to the laws of quantum physics, it has both states at once and exists in something called a quantum superposition. It’s worth pointing out that scientists have observed that superpositions exist, and have devised experiments to show it. That becomes important in a minute.
So you have one polarized photon in a superposition of being both vertically and horizontally polarized at once, and you have two scientists: Wigner, and Wigner’s friend. Wigner is performing an experiment to show that the photon is in a superposition and has all possible states of polarization. In Wigner’s reality this is now “fact.”
Meanwhile, Wigner’s friend has sneaked in, without Wigner’s knowledge, to another lab looking at the same photon. Wigner’s friend measures which polarized state it’s in, which snaps it out of superposition and into a definitive state, and records the result without ever telling Wigner. They then compare notes and find that something very strange has then happened. At the exact same time, Wigner and his friend recorded two different versions of reality and they are both correct.
Until now, that was simply a thought experiment. Just last week, however scientists at Heriot-Watt University in Edinburgh say they have performed a real life test of the Wigner’s friend experiment, and it worked out exactly as the thought experiment said it would. I’ll use the description of the experiment published in the MIT Technology Review:
The breakthrough that Proietti and co have made is to carry this out. “In a state-of-the-art 6-photon experiment, we realize this extended Wigner’s friend scenario,” they say.
They use these six entangled photons to create two alternate realities—one representing Wigner and one representing Wigner’s friend. Wigner’s friend measures the polarization of a photon and stores the result. Wigner then performs an interference measurement to determine if the measurement and the photon are in a superposition.
The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes, just as Wigner predicted.
If this experiment turns out not to have missed something, some loophole they were unaware of, then the implications are staggering. It means that the fundamental idea that there is one shared reality, that things that exist, exist for everyone, must be wrong. What does this say about strange phenomena like, say, the Mandela effect? According to the MIT Technology Review, the next step for these scientists is to push the idea further and see how drastically different they can make the two coexisting realities. As if the world wasn’t already confusing enough, leave it to quantum physics to make it even more nonsensical.