(ORDO NEWS) — What is reality? And who can answer this question? Last year, scientists from Heriot-Watt University in Scotland tested an interesting experiment, the results of which suggest that objective reality may not exist. Despite the fact that once this idea was just a theory, now researchers were able to transfer it to the walls of the university laboratory, and therefore test it. Since in the quantum world measurements from different positions give different results, but at the same time are equally correct, the experiment carried out showed that in the world of quantum physics, two people can observe the same event and different results; however, neither of these two events can be perceived as wrong. In other words, if two people see two different realities, then they cannot agree which one is correct.
Quantum mechanics is a branch of theoretical physics that describes the basic properties and behavior of atoms, ions, molecules, electrons, photons, condensed matter, and other elementary particles.
Wigner’s friend paradox
In 1961, Nobel Prize laureate in physics Eugene Wigner seriously questioned what objective reality is. The scientist proposed one of the strangest experiments in quantum mechanics, which involved the idea that two people could observe two different realities and neither of them would technically be wrong. But how?
In a thought experiment called Wigner’s friend paradox, two scientists in a laboratory study a photon – the smallest quantitative unit of light. It is noteworthy that this polarized photon, when measured, can have either horizontal polarization or vertical polarization. But before measurement, according to the laws of quantum mechanics, a photon exists in both polarization states simultaneously – in the so-called superposition.
So, Wigner imagined his friend in another laboratory measuring the state of this photon and memorizing the result, while Wigner himself observes from afar. At the same time, Wigner does not have any information about the measurement of his friend, and therefore he is forced to assume that the photon and its measurement are in a superposition of all possible experimental results.
But this is in sharp contrast to the point of view of Wigner’s friend, who actually measured the polarization of the photon and recorded it! The friend may even call Wigner and tell him that the measurement has been made (provided that the result is not revealed). Thus, we get two realities that contradict each other, which casts doubt on the objective status of the facts established by two observers.
It is noteworthy that until 2019 – until the Swedish scientists did the same experiment in the laboratory – Wigner’s friend’s paradox was purely a thought experiment. Just like the world famous experiment proposed by the Austrian theoretical physicist Edwin Schrödinger.
Schrödinger’s cat is a thought experiment describing the absurdity of quantum mechanics. Imagine you have a cat and a box. In the box you put a cat, a radioactive substance and a special mechanism that opens a flask with poison. In the event of a decay of a radioactive atom in a closed box – and this can happen at any moment – the mechanism will open the container with poison and the cat will die. But you can only find out whether a radioactive atom has decayed or not, you can only look into the box. Up to this point, according to the principles of quantum physics, the cat is both alive and dead, that is, it is in superposition.
Is there no objective reality?
The researchers used six entangled photons to create two alternative realities in the lab. One reality represented the reality of Wigner, the other the reality of his friend. Wigner’s friend measured the polarization of the photon and saved the result, after which Wigner himself performed an interference measurement to determine whether the measurement and the photon were in superposition.
The results obtained by the team of scientists were mixed. It turned out that both realities can coexist, even if they lead to irreconcilable results – just as Eugene Wigner predicted. But can they be reconciled?
The idea that observers can eventually reconcile their measurements of some fundamental reality is based on several assumptions. First, universal facts do exist and observers can agree on them. Second, the choice that one of the observers makes does not affect the choice that the other observers make — this assumption physics calls locality. So if there is an objective reality that everyone can agree with, then all these assumptions are true.
But the results of the work of scientists from Heriot-Watt University, published in the journal Science Advances, indicate that objective reality does not exist. In other words, the experiment suggests that one or more assumptions – the idea that there is a reality that we can agree with, the idea that we have free choice, or the idea of locality – must be wrong.
“The scientific method relies on universally agreed facts established by multiple measurements, regardless of who made the observations,” the researchers write in their work.
I don’t know about you, but my head is spinning, because the results obtained provide real evidence that when it comes to the field of quantum physics, such a thing as objective reality cannot exist.
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