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posted by janrinok on Wednesday September 24 2014, @12:45AM   Printer-friendly
from the rest-of-the-person-will-teleport-along-shortly... dept.

Physicists at the University of Geneva (UNIGE) ( http://cms.unige.ch/gap/quantum/wiki/research:quantum_communication:teleportation ) have succeeded in teleporting the quantum state of a photon to a crystal over 25 kilometres of optical fibre. The experiment, carried out in the laboratory of Professor Nicolas Gisin, constitutes a first, and simply pulverises the previous record of 6 kilometres achieved ten years ago by the same UNIGE team. Passing from light into matter, using teleportation of a photon to a crystal, shows that, in quantum physics, it is not the composition of a particle which is important, but rather its state, since this can exist and persist outside such extreme differences as those which distinguish light from matter.

http://www.sciencedaily.com/releases/2014/09/140921145007.htm

 
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  • (Score: 2) by wonkey_monkey on Friday September 26 2014, @12:32PM

    by wonkey_monkey (279) on Friday September 26 2014, @12:32PM (#98553) Homepage

    My whole idea is, if you have three entangled particles in a superposition, and you explicitly collapse the wave function for one of them, the wave function of the remaining two should also collapse.

    Yes, it will, but measuring one of the other two photons also collapses the wavefunction. There's no information to be gleaned.

    As I understood the explanation, the Bell theorem should prove the superposition on a statistical base, not for a single photon.

    It proves it for all photons, everywhere, always - it's not true for some groups of photons and untrue for others.

    According to the link I posted, there is an experiment with a probability of 50% for a certain outcome when the state is predefined, and 55% probability when the particles are in a superposition.

    "Being in a predefined state" is not the opposite of "being in a superposition." When you say "when the state is predefined" - well, it never is, that's what the Bell theorem's experiments tell us. You can only "force" a photon into a definite (not predefinite) state along a single axis. As soon as you do, the state along all other axes is undefined (albeit probabilistically correlated with the original measurement, depending on the new axis). Measure along the same axis again, and you'll get the same measurement. Measure along a nearby axis, and you'll probably get the same measurement, but maybe not. And as soon as you make that second measurement, spin along the original axis becomes undefined (albeit probabilistically correlated to the new axis in the same manner as before).

    "Being in a predefined state" was one way of explaining the quantum behaviour of certain particle properties, but the Bell theorem experiments proved it not to be true.

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