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Spathi
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https://backreaction.blogspot.com/2022/02/has-quantum-mechanics-proved-that.html
Physicists have shown that objective reality doesn’t exist. This is allegedly an insight derived from quantum mechanics. And not only this, it’s been experimentally confirmed. Really? How do you prove that reality doesn’t exist? Has it really been done? And do we have to stop saying “really” now? That’s what we’ll talk about today.
Okay, so that was Wigner’s friend in the 1960s. You can’t experimentally test this, but in 2016 Daniela Frauchinger and Renato Renner proposed another thought experiment that moved physicists closer to experimental test. This has been dubbed the “Extended Wigner’s Friend Scenario.”
In this thought experiment you have two Wigners, each of whom has a friend. We will call these the Wigners and the Alices. The Alices each measure one of a pair of entangled particles. As a quick reminder, entangled particles share some property but you don’t know which particle has which share. You may know for example that the particles spins must add up to zero, but you don’t know whether the left particle has spin plus one and the right particle spin minus one, or the other way round.
It is unclear for me, why from these experiments the tabloids made the conclusion that "the reality does not exist"? Does the essence of this experiment lie in the fact that it confirmed the Wigner's friend paradox, or is it more about something fundamentally new? I understand the Wigner's friend's paradox in such a way that when a scientist opens a box with a cat, a superposition is formed of two scientists observing a living or dead cat, in other words, two "parallel worlds". It seems there is nothing here too strange, that “refutes the existence of objective reality”. Or maybe the main idea is that simply that there are two realities in this case?So the Alices each measure an entangled particle. Now the thing with entangled particles is that if their measurements don’t collapse the wave-function, then now the two Alices are entangled. Either the left one thinks the spin was up and the right one thinks it’s down, or the other way round. And then there’s the two Wigners, each of which goes to ask their friend something about their measurement. Formally this “asking” just means they do another measurement. Frauchinger and Renner then show that there are combinations of measurements in which the two Alices cannot agree with the two Wigners on what the measurement outcomes were.