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Technology Stocks : Quantum Computing -- Ignore unavailable to you. Want to Upgrade?

To: Cisco who wrote (9)	7/9/2001 4:22:38 AM
From: Vendit™	Read Replies (1) \| Respond to of 65

There is evidence that Einstein may have helped open the door to prove that E=mc2 is not absolute. "As if superposed values and probability waves were not counterintuitive enough, another strange phenomenon is prominent in the new science of quantum information. In the '30s, scientists fiercely debated whether what quantum mechanics predicted had a real existence or whether its strangeness was due to some deficiency in the theory. In particular, Albert Einstein could not believe that the universe was built as quantum mechanics claimed. So, together with his colleagues Boris Podolsky and Nathan Rosen, he devised a thought experiment to find holes in the new theory. The thought experiment centers on the behavior of pairs of particles that, according to quantum theory, are joined together--entangled--in a profound way that has no analog in the classical world. Prod one, and it seems the other instantly feels the influence, no matter how far away it might be. The three scientists pointed out that this process would have to involve a faster-than-light signal passing between the particles--an impossibility. Their conclusion became known as the EPR (Einstein-Podolsky-Rosen) paradox and the entangled particles as EPR pairs. The debate was resolved by John Bell (Art Bell's brother <g>), a theorist at CERN, the European laboratory for particle physics near Geneva, and the French physicist Alain Aspect. They proved that the Siamese twins of the quantum world, EPR pairs, indeed behave in the way predicted by quantum mechanics. However, the experiment also showed that there is no faster-than-light signal and that entanglement cannot be used for superluminal communication. Rather than communicating, EPR pairs share the same existence, the same destiny, if you like. Entanglement is now one of the key phenomena exploited in quantum information processing. Today the EPR experiment is performed almost daily around the world."

To: Cisco who wrote (9)	7/9/2001 4:45:37 AM
From: Vendit™	Respond to of 65

This is from some research papers which are widely available. "The first big breakthrough for scientists building actual quantum computers came in the mid-'90s, when they discovered how to carry out calculations using the techniques of nuclear magnetic resonance (NMR). The key idea was that a single molecule can act like a tiny computer. Information is stored in the orientation of nuclear spins in the molecule, each nucleus holding one qubit. And the interaction between the nuclear spins, known as spin-spin coupling, serves to mediate logic operations. In a strong magnetic field, these nuclei precess around the direction of the magnetic field at frequencies that depend on their chemical environment. For instance, in a 9.3-tesla field, a carbon-13 nucleus in a chloroform molecule precesses at about 100 MHz. By zapping the molecule with radio waves tuned to these resonant frequencies, it is possible to manipulate each nucleus individually to carry out logic operations. The manipulation might involve flipping a nucleus from a 1 to a 0, a so-called one-qubit operation or single-bit rotation; or it might involve two linked nuclei in a two-qubit operation, in which the value of one nucleus is flipped in a way that depends on the value of the other. Chloroform made with the carbon-13 isotope is a good example of a molecule that can act as a two-qubit quantum computer, because its hydrogen and carbon-13 nuclei can be addressed individually by the radio waves. A quantum calculation is then carried out by encoding a program--a sequence of one- and two-qubit operations--as a series of RF pulses. The results are then read out by listening for the magnetic induction signal generated by the precessing nuclei at the end of the calculation. That signal indicates the orientation of the nuclear spin. Nuclear magnetic resonance sounds like the dream solution to a thorny problem. Nuclei are naturally isolated from the noise of the outside world and so can maintain coherence for many seconds, enough time to perform hundreds of logic operations. In addition, NMR is a mature technology, having been used over many years for imaging and chemical analysis. But the technique has some severe limitations. Single molecules do not produce a signal strong enough to be observed. Instead, NMR experiments must involve huge numbers of molecules (of the order of 10-23rd) so that their combined magnetic induction signal is large enough to be picked up. (These molecules are usually distributed in a solvent, so the first quantum computers actually have liquid hearts.)"

To: Cisco who wrote (9)	7/9/2001 4:59:22 AM
From: Vendit™	Read Replies (2) \| Respond to of 65

Teleportation of photons has already become a reality. "Bennett and his colleagues had to wait four years to see their predictions verified. In 1997, in a small room at the University of Innsbruck, in Austria, a group of physicists led by Anton Zeilinger performed the first teleportation experiment. Zeilinger's travelers were photons and he was sending them only a meter or so, from one side of the lab to the other. Today, more than three years later, Zeilinger is working on the next step, which is to teleport photons over distances of a kilometer. Soon after Zeilinger's breakthrough, Cirac and Zoller proposed that teleportation could become the basis of a kind of quantum Internet. And in March of 2000, Seth Lloyd and Selim Shahriar at MIT and Philip Hemmer at the U.S. Air Force Research Laboratory, in Lincoln, Mass., suggested sending entangled photons over optical fibers to nodes containing cold atoms that would absorb the photons and so store the entanglement. This entanglement could then be used for error correction, teleportation, and various other valuable applications. A number of groups are working on this idea, including Jeff Kimble at the California Institute of Technology and Eli Yablonovitch at the University of California at Los Angeles. They hope to have a three-node network running within 10 years."