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This brand new published result (nature):

Experimental non-classicality of an indivisible quantum system
by Radek Lapkiewicz, Peizhe Li, Christoph Schaeff, Nathan K. Langford, Sven Ramelow, Marcin Wieśniak & Anton Zeilinger

(see here, for a more popular article about it see here; also for a pre-print see the ArXiv here)

seems to support the Copenhagen interpretation.

My question
Does this definitely rule out the many-worlds interpretation - or are there still loopholes? How could a many-worlds interpretation of this experiment possibly look like (if possible)?

Thank you

Because I obviously created some confusion, how I came to that question: at the end of the NewScientist-article it says:

Niels Bohr, a giant of quantum physics, was a great proponent of the idea that the nature of quantum reality depends on what we choose to measure, a notion that came to be called the Copenhagen interpretation. "This experiment lends more support to the Copenhagen interpretation," says Zeilinger.

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1 Answer 1

up vote 8 down vote accepted

They don't make any claim in the paper about interpretations of quantum theory, either for the Copenhagen interpretation or against many-worlds interpretations. Nor does the Phys. Rev. Lett. 101, 20403 (2008) that they cite as their principal theoretical source. The Vienna group's stated intention here, as, I think, in a number of papers over the last few years, has been to try to rule out contextual classical particle models for experiments. This is to me something of a straw man, but they have been hacking away at it.

I was going to ask that you expand your Question to say why you think this experiment supports the Copenhagen interpretation over other interpretations, because I do not see that to be the case, but I finally saw the off the cuff remark to that effect from Zeilinger at the very end of the New Scientist article [you should have cited this]. That's definitely not enough to rule out many-worlds interpretations without a much more substantial argument. There isn't, so far, enough of an argument to have loopholes in it.

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If Zeilinger means that the experiment supports the Copenhagen interpretation as opposed to many-worlds, that's complete nonsense. Many-worlds and Copenhagen make precisely identical predictions for this experiment. From the context of the New Scientist article, it seems that Zeilinger might mean that the results support the Copenhagen interpretation as opposed to some unspecified hidden-variables theory. That's true, but it'd be clearer simply to say that the results support quantum mechanics as opposed to hidden-variables theories. –  Ted Bunn Jun 23 '11 at 14:21
@Ted, agreed. I guess he said something that appealed to the New Scientist reporter's POV. It's something that I suppose wouldn't make the cut in an article. In particular, there's not even a hint of it in the Nature article. –  Peter Morgan Jun 23 '11 at 14:27
Sadly, this is par for the course for New Scientist. I'd be willing to be that the confusion is not Zeilinger's fault. –  Ted Bunn Jun 23 '11 at 15:37
@Ted, I hope Zeilinger actually said it, otherwise New Scientist is totally outside the journalistic fold. They cite him as saying it, “"This experiment lends more support to the Copenhagen interpretation," says Zeilinger.” At face value, he got himself into this. He's experienced enough with journalists to know that such a money quote may get out of his control. I doubt it will haunt Zeilinger for more than a few days, and it may perhaps be noted nowhere except here, but perhaps it's a nail for the New Scientist. –  Peter Morgan Jun 23 '11 at 15:53
They talk about this being bad for 'hidden variable theories' - when I think that they mean its bad for 'local hidden variable theories'. There are non - local hidden variable theories which have the exact same mathematics as regular QM. –  Tom Andersen Oct 17 '11 at 1:57

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