Nonlocality of a Single Particle: A Scheme Without Objections

[Ivan Seeking]

...Now, Jacob Dunningham from the University of Leeds and Vlatko Vedral from the University of Leeds and the National University of Singapore have modified Hardy’s scheme, publishing their results in a recent issue of Physical Review Letters. By eliminating all unphysical inputs, their scheme allows for a real experiment, and ensures that only a single particle exhibits nonlocality. Plus, Dunningham and Vedral’s scheme not only applies to single photons, but to atoms and single massive particles, as well.

“The greatest significance of this work is that it shows how superposition and entanglement are the same ‘mystery,’” Dunningham explained to PhysOrg.com. “Feynman famously said that superposition is the only mystery in quantum mechanics, but more recently entanglement has been widely considered as an additional fundamental feature of quantum physics. Here we show that they are one and the same.” [continued]

http://www.physorg.com/news113824784.html

 

[ZapperZ]

The "demonstrated" part is a bit misleading. All they did was to reformulate the Hardy criteria that did not have the part that GHZ objected to. We still have to wait for an experiment using such a scheme.

Zz.

 

[Ivan Seeking]

Sure enough! The title and a quick read led me to think they had actually done the experiment. I'll change the word "demonstrated" to "scheme".

 

[DrChinese]

A minor quibble: This demonstrates "non-locality" no more - and no less - than traditional Bell tests with entangled particles. The issue, as is well known, is that such experiments show that either locality OR realism must be rejected to match the predictions of QM. It does not say which of these two must go. The title of the article could have been "Non-Realism of a Single Particle" just as easily - and just as accurately.

 

[Ivan Seeking]

Okay, but I'm not changing the title again.

 

[cesiumfrog]

That's a bit superfluous: I don't think many physicists will contemplate abandoning realism at this stage. (Heck, could I even speak of other physicists if I did?)

Very interesting claim, that entanglement is just superposition (a classical wave effect.. basically reduces most of "the mystery" to ol' Fourier math), I'm keen to see how this is received (particular by Zeilinger et al).

 

[ueit]

Just like all the other experiments of this type it "proves" non-locality (or non-realism) only if other, supplementary assumption is hold true. One must assume that the particles' properties, as they leave the source, are not influenced by the presence of the experimental setup (prism, detectors, Alice & Bob, etc). This is hardly an acceptable hypothesis.