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2Physics Quote:
"Can photons in vacuum interact? The answer is not, since the vacuum is a linear medium where electromagnetic excitations and waves simply sum up, crossing themselves with no interaction. There exist a plenty of nonlinear media where the propagation features depend on the concentration of the waves or particles themselves. For example travelling photons in a nonlinear optical medium modify their structures during the propagation, attracting or repelling each other depending on the focusing or defocusing properties of the medium, and giving rise to self-sustained preserving profiles such as space and time solitons or rapidly rising fronts such as shock waves." -- Lorenzo Dominici, Mikhail Petrov, Michal Matuszewski, Dario Ballarini, Milena De Giorgi, David Colas, Emiliano Cancellieri, Blanca Silva Fernández, Alberto Bramati, Giuseppe Gigli, Alexei Kavokin, Fabrice Laussy, Daniele Sanvitto. (Read Full Article: "The Real-Space Collapse of a Two Dimensional Polariton Gas" )

Monday, November 20, 2006

Breakthrough in Quantum Computing

Christoph Boehme of University of Utah works with equipment used to detect magnetic "spins" of phosphorus atoms (photo courtsey: John Lupton/University of Utah)

A US-German team of scientists could advance a step closer to designing super fast quantum computers with their recent experiment showing how a phosphorus-and-silicon quantum computer might work. Their study to be published in the December issue of Nature Physics shows it's possible to read data stored in the form of the magnetic "spins" of phosphorus atoms. They have demonstrated experimentally that the nuclear spin orientation of phosphorus atoms embedded in silicon can be measured by very subtle electric currents passing through the phosphorus atoms.

Digital computers of the current world rely on information transmitted by flowing electricity in the form of electrons, which are negatively charged subatomic particles. Transistors in these computers are electrical switches that store data as "bits" in which "off" (no electrical charge) and "on" (charge is present) represent one bit of information: either 0 or 1. On the other hand, in a quantum computer, one quantum bit or 'qubit' could be both 0 and 1 at the same time. Quantum computers rely on the fact that the smallest particles can be in different places at the same time abiding by some seemingly strange laws of quantum mechanics.

The scientists harnessed the unique properties of quantum physics by "doping" silicon — the semiconductor used in digital computer chips — with atoms of phosphorus. Next they applied electric current to read and process the data stored in the "spins" of those phosphorous atoms' nuclei. which may register a value of 0 and 1 simultaneously. In essence, the team's study was about a successful "reading" of the net spin of 10,000 of the electrons and nuclei of phosphorus atoms near the surface of the silicon.

This is a major step in right direction but, like any other revolution in science and technology, it needs to go through lot of developments and wait for progress in other related aspects before a quantum computer becomes a reality.

Team of scientists: Christoph Boehme, University of Utah, USA; Klaus Lips at the Hahn-Meitner Institute, Berlin with graduate students Andre Stegner and Hans Huebl; Martin Stutzmann and Martin Brandt, Technical University of Munich.

Background Reading:
The Quantum Computer: An Introduction" by Jacob West, Caltech, USA
"Quantum computation: a tutorial" by Samuel L. Braunstein, University of York, York, UK.
Wikipedia page on quantum computer

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