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From physnews@aip.org Wed Dec 10 16:59:59 1997 Date: Wed, 10 Dec 97 14:35:44 EST Subject: update.350
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 350 December 10, 1997 by Phillip F. Schewe and Ben Stein
QUANTUM TELEPORTATION has been experimentally demonstrated by physicists at the University of Innsbruck (Anton Zeilinger, 011-43-676-305-8608, anton.zeilinger@ uibk.ac.at; Dik Bouwmeester, Dik.Bouwmeester@uibk.ac.at). First proposed in 1993 by Charles Bennett of IBM (914-945-3118), quantum teleportation allow physicists to take a photon (or any other quantum-scale particle, such as an atom), and transfer its properties (such as its polarization) to another photon--even if the two photons are on opposite sides of the galaxy. Note that this scheme transports the particle's properties to the remote location and not the particle itself. And as with Star Trek's Captain Kirk, whose body is destroyed at the teleporter and reconstructed at his destination, the state of the original photon must be destroyed to create an exact reconstruction at the other end. In the Innsbruck experiment, the researchers create a pair of photons A and B that are quantum mechanically "entangled": the polarization of each photon is in a fuzzy, undetermined state, yet the two photons have a precisely defined interrelationship. If one photon is later measured to have, say, a horizontal polarization, then the other photon must "collapse" into the complementary state of vertical polarization. In the experiment, one of the entangled photons A arrives at an optical device at the exact time as a "message" photon M whose polarization state is to be teleported. These two photons enter a device where they become indistinguishable, thus effacing our knowledge of M's polarization (the equivalent of destroying Kirk).What the researchers have verified is that by ensuring that M's polarization is complementary to A's, then B's polarization would now have to assume the same value as M's. In other words, although M and B have never been in contact, B has been imprinted with M's polarization value, across the whole galaxy, instantaneously. This does not mean that faster-than-light information transfer has occurred. The people at the sending station must still convey the fact that teleportation had been successful by making a phone call or using some other light-speed or sub-light-speed means of communication. While physicists don't foresee the possibility of teleporting large-scale objects like humans, this scheme will have uses in quantum computing and cryptography. (D. Bouwmeester et al., Nature, 11 Dec 1997; see also www.aip.org/physnews/graphics)
DO EARTHQUAKES HAVE ELECTRICAL PRECURSORS? The
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