Post by Brett Hallhttp://www.scientificamerican.com/article.cfm?id=quantum-delayed-choice
"New experiments demonstrate that photons not only switch from wave to particle and back again but can actually harbor both wave and particle tendencies at the same time. In fact, a photon can run through a complex optical apparatus and disappear for good into a detector without having decided on an identity—assuming a wave or particle nature only after it has been destroyed."
"Physicists have shown in recent years that a photon "chooses" whether to act as a wave or a particle only when forced. If, for instance, a photon is steered by a beam splitter (a kind of fork in the optical road) onto one of two paths, each leading to a photon detector, the photon will appear at one or the other detector with equal probability. In other words, the photon simply chooses one of the routes and follows it to the end, like a marble rolling through a tube"
I like how in that paragraph "chooses" becomes just chooses.
"Quantum information researcher Seth Lloyd of the Massachusetts Institute of Technology dubbed the phenomenon "quantum procrastination," or "proquastination" in a commentary for Science accompanying the two research papers. "In the presence of quantum entanglement (in which outcomes of measurements are tied together)," he wrote, "it is possible to hold off making a decision, even if events seem to have already made one."
The new experiments add another wrinkle to the warped world of quantum mechanics, where a photon can be seemingly whatever it wants, whenever it wants. "Feynman called it the one true mystery of quantum mechanics," Shadbolt says of wave–particle duality. "It's deeply, deeply strange. Quantum mechanics is deeply weird, completely without classical analogue, and we just have to accept it as such.""
It seems that everything would be so much more clear if only they read FoR and BoI and embraced the multiverse.
What do the physicists here think about this experiment? What's it actually showing? I didn't get it...I only "got" that they seemed to be all doe-eyed about the jargon of wave-particle duality and the "woo".
The experiments are described in the papers here
http://arxiv.org/abs/1206.4348
http://arxiv.org/abs/1205.4926
Both of them are variants on the EPR experiment.
In one of the experiments two photons are entangled in their polarisation |H>|H>+|V>|V> ((horizontal H, vertical V). One of them (photon 1) is put through a detector whose effect is polarisation dependent - it acts like it contains a beamsplitter in V but not in H. When you compare the results afterward you find that when photon 2 (the other photon) is in V then the detector acts like it contains a beamsplitter and the results look like a photon undergoing interference in H they don't look like that. When the results look interferey they call this wave behaviour, when the results don't look interferey they call it particle behaviour.
The other experiment is similar except that
(1) The experiment consists of multiple linked interferometers.
(2) The photons interact and the amount of entanglement between them depends on the state of both of them at the time of the interaction.
(3) Specifically, the entanglement depends on which branches of the sub-interferometers they are on.
Neither of them are tests of the Copenhagen interpretation because it is a bad explanation which can be ruled out without experimental testing. Also, it's not clear how to experimentally test a theory that claims objective reality doesn't exist.
It's interesting that they talk about accepting quantum mechanics and then utter vague, ritualistic gibberish instead of looking seriously at what the theory says about how the world actually works.
Alan
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