# Quantum experiment showed that objective reality does not exist

As early as 1961, physicist and Nobel laureate Eugene Wigner laid out a thought experiment, which demonstrated one of the least well-known paradoxes of quantum mechanics. The experiment shows how the strange nature of the universe allows two monitors - say, Wigner and other Wigner - experiencing different realities. Since then, physicists use a thought experiment "Wigner's friend" to investigate the nature of measurement and debate about whether there are objective facts.

First, tell about Wigner thought experiment:

Suppose that two people at the same time open the box with the cat Schrödinger. If the result (the collapse of the wave function) chooses the observer, it implies an idealistic solution, if two observers make different choices - there is a problem. If we refer to one of two outcomes, the choice can only do one of the observers and supporters of realism rightly consider this decision unsatisfactory.

"The paradox of Wigner's friend, formulated by the physicist Eugene Wigner, the following occurs: Suppose that instead of to watch the cat, Wigner asks his friend to do it. His friend opens the box, sees a cat, and then reports the results of his observations Wigner. At this stage we can say that Wigner just updated the reality that includes his friend and a cat. Here is a paradox: whether the cat is alive or dead when Wigner her boyfriend watched, but he said the result of observation? Say that when the Wigner one watched the cat, her condition did not collapse, it is to say that his friend was in an unconscious state until Wigner was not asked - that the mind of his friend could not decide alive cat or dead, without prompting from the Wigner " .

The paradox has become important because scientists are conducting experiments to determine the objective facts. But if they are faced with different realities as they agree on what could be these facts? Wigner thought experiment has never been anything more - just a thought experiment.

But last year, physicists have noticed that the latest advances in the field of quantum technologies have allowed to play another test in a real experiment Wigner In other words, it is possible to create different realities and compare them in the laboratory, in order to find out whether it is possible to reconcile them.

## Is there an objective reality?

Today Massimiliano Proyetti from Heriot-Watt University in Edinburgh and some of his colleagues have said that for the first time conducted the experiment: create different realities and compare them. And they came to the conclusion that Wigner was right: these realities can be bitter as it is impossible to reach a consensus on the objective facts in the experiment.

Initially thought experiment started with a Wigner polarized photon, which when measured can have a horizontal or vertical polarization. But before the measurement, according to the laws of quantum mechanics, the photon exists in both polarization states at the same time - the so-called superposition.

Wigner imagined friend in another laboratory, which measures the state of the photon and stores the result, while Wigner watching from afar. Wigner had no information about his friend's dimensions and therefore have to assume that the photon and its measurement is in a superposition of all possible outcomes of the experiment.

Wigner may even conduct an experiment to determine if there is a superposition of this or not. A kind of interference experiment, which shows that the photon and measurement really are in superposition. In terms of Wigner, this "fact" - there is a superposition. This fact suggests that the measurement could not be carried out.

But his friend would disagree, as he measured the photon polarization and recorded it. Each may even call Wigner and tell that the measurement has been made (with the proviso that the result is not disclosed).

Two realities contradict each other. "This casts doubt on the objective status of facts established by the two observers," says Proyetti.

That is the theory, but in the past year Caslano Bruckner of the University of Vienna in the Australian came up with a way to recreate the "Wigner's friend" in the laboratory using methods including trapping many particles simultaneously.

Breakthrough Proyetti also consisted in the fact that they did it in fact. They have implemented advanced scenario "Wigner's friend" in a modern experiment with six photons.

Six photons were entangled to create two alternate realities - one representing Wigner, and the second - Wigner other. Wigner's friend measures the polarization of a photon and stores the result. Wigner then performs a measurement of interference in order to understand whether the measurement of the photon in a superposition are.

The experiment gave mixed results. It turns out that both realities can co-exist, even if they give irreconcilable results, as predicted by Wigner. This raises some interesting questions that encourage the physicists to reconsider the nature of reality.

The idea that observers can eventually reconcile their measurements in any fundamental reality, is based on several assumptions. First, universal facts do exist, and observers can agree on them. But there are other suggestions. One of them is the fact that observers are free to do any monitoring, what they want. And one more thing: a choice that makes one observer, does not affect the selection of other observers. This assumption of physics is called locally.

If there is an objective reality with which everyone can agree, all these assumptions are true.

But the result Proyetti and his colleagues suggest that objective reality does not exist. In other words, the experiment suggests that one or more of the assumptions - that there is a reality with which we agree; that there is freedom of choice; or local - should be correct.

Of course, there is another option. Option that there is a loophole, which the experimenters have missed. In fact, physicists have tried to close the loopholes in such experiments for many years, but they recognize that it may never be able to close them all.

However, the work has important implications for science. The next step - to go further: to create experiments that create more bizarre alternate reality, which can not be reconciled. Where it will lead us, no one knows.

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