No non-locality after all in QM?

[StevieTNZ]

At least, according to this paper - http://arxiv.org/ftp/quant-ph/papers/0206/0206190.pdf - nonlocality isn't real in QM.

Thoughts?

 

[SpectraCat]

It sure looks like nonsense to me ... it starts on the fringe of local realism, and then seems to wander off into the enchanted fairyland of make-believe physics. It is a short paper full of qualitative, descriptive arguments, with very little math to support them, and a vaguely described experiment. These features should get your skeptical hackles up.

Furthermore, a similar experiment has been done, and found to contradict the author's predictions. The experiment described here:

http://arxiv.org/abs/0909.4908

is not precisely the same as in the paper you linked, but there are sufficient similarities for me to conclude that the conclusions in the paper you linked are just wrong. For examples, the photons are clearly corrlated in a fundamentally non-local way, and in fact the authors show that the experimental results are consistent with the theory of non-local modulation, which they develop to include the effects of finite measurement precision appropriate to describe their experimental results. Note also that the experimental paper was published in a (fairly prestigious) physics journal (Phys. Rev. Lett. 103, 163601 (2009)).

 

[my_wan]

I am a realist and I do not see the significance of this paper in addressing the issues realism poses. Taking a realist stance and hand waiving away the issues such a stance poses is not the same thing.

 

[DrChinese]

At least, according to this paper - http://arxiv.org/ftp/quant-ph/papers/0206/0206190.pdf - nonlocality isn't real in QM.

Thoughts?

The hypothesis is overreaching - that you can somehow "disprove" nonlocality.

But as is mentioned, the experimental support is a joke. QM properly predicts the actual results of all spacelike separated experiments. You can call that proof of nonlocality or not, depending on your interpretation. For the experiment to mean what he says it does, it would need to contradict QM.

 

[my_wan]

The hypothesis is overreaching - that you can somehow "disprove" nonlocality.

But as is mentioned, the experimental support is a joke. QM properly predicts the actual results of all spacelike separated experiments. You can call that proof of nonlocality or not, depending on your interpretation. For the experiment to mean what he says it does, it would need to contradict QM.

When you say "For the experiment to mean what he says" what are you taking it to say? I am presuming the lack of a "state reduction". On that presumption I would say that a "state reduction" is itself an "interpretation" rather than "what QM says". QM does not care what interpretation anybody chooses, state reduction or not. Hence, since it is itself merely an interpretation, it cannot in itself contradict QM. That the paper failed to make a reasonable argument is immaterial to that point.

It seems that a lot lot of argument is geared around: Since interpretation X is valid interpretation Y is wrong... No no no.. Since interpretation Y is valid interpretation X is wrong. If your claim that of a contradiction of QM goes deeper than 'interpretation' please explain.

 

[chwie]

Is good to read the paper I have a problem with the non-locality of QM specially the collapse of the state. I have a post here about it https://www.physicsforums.com/showthread.php?t=509443.

My argument is that if you have non-local behavior in quantum mechanics such that two events that are separated spacelike have a relation of cause and effect, then there is a problem. I have two examples in the post that I did before. The non-local behavior of quantum mechanics is not a surprise at first, for example during a lot of time classical mechanics was non-local (gravitational force was non-local), was relativity the one that show that classical mechanics is a local theory. Now quantum mechanics is not a relativistic theory and this non-local behavior of quantum mechanics have not been studied a lot in a relativistic quantum theory. The measurement in quantum mechanics is ill defined, Decoherence have done a lot to understand how we can solve this problem (we can't ignored the environment) but that doesn't mean that our conception of quantum mechanics are wrong. There is not a real evidence of the non-local behavior of quantum mechanics, just that using our ill defined measurement and the tensor product we expect to have a non-local behavior (violations of bell inequality doesn't show non-local behavior) ( I am excluding unitary transformations). If somebody can argued it, I want to hear, because I really don't see the light at the end of the tunnel. For example i don't know of any example of non-locality of quantum mechanics that can be deduced directly from QED which is a relativity and quantum mechanical theory (probably is that in QED non unitary transformation are not that common). If somebody knows one, please give me a link for the paper or cite the reference. That will be an interesting case to study. I believe in some of the features of the non-locality of quantum mechanics, specially because of decoherence. Now to related non-local unitary transformations to the non-local behavior of quantum mechanics for me is a mistake. Unitary transformations are ok for me because I don't see a problem in it.