A paradoxical thought experiment was devised in 1961 by the physicist Eugene Wigner. Similar to Schrödinger's cat, the so-called "friend of Wigner" postulates that two people can experience two different realities of the same physical phenomenon.
To begin with, we have a quantum system with two superimposed states. Wigner's friend is in a laboratory doing an experiment with an interlaced photon system; once you make a measurement, the system will collapse and the photon will exist in one of two states: a vertical polarization or a horizontal polarization. But, for Wigner, who is outside the laboratory, without knowing the result of the observation, the quantum state will continue in superposition. You can even perform an interference experiment and verify that the photons are still in superposition. So Wigner and his friend will have two coexisting objective realities.
This theoretical experiment is not easy to execute but, apparently, the physicist Massimiliano Proietti and his colleagues have managed to put Wigner's paradox to the test - and it seems that the Nobel Prize in Physics was right -. The physicists managed to build an experiment of six intertwined photons to create two alternative realities. In the experiment, a physicist who takes the role of Wigner's friend performs the polarization measurement of the photon and stores the result. Another physicist, Vicar of Wigner, then makes the measurement of interference.
The experiment produces a disturbing result: both realities coexist, although they produce irreconcilable results. As the MIT magazine says:
the results of Proietti and company suggest that objective reality does not exist. In other words, the experiment suggests that one or more of the assumptions-the idea that there is a reality on which we can agree, the idea that free will exists or the idea of locality-must be wrong.
Either way, they leave us in a strange universe: either a universe that depends on our observing consciousness, a deterministic universe or a universe where things are connected at a distance.