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Topic: Quantum computer

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	Quantum computer - Wikipedia, the free encyclopedia
		In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, it is measured by qubits.
		The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that quantum mechanisms can be devised and built to perform operations with this data.
		Quantum computers are different from classical computers such as DNA computers and computers based on transistors, even though these may ultimately use some kind of quantum mechanical effect (for example covalent bonds).
	en.wikipedia.org /wiki/Quantum_computer (3339 words)

	Reference.com/Encyclopedia/Quantum computer
		In a classical (or conventional) computer, data are measured by bits; in a quantum computer the data are measured by qubits.
		In quantum mechanics, the state of a physical system (such as an electron or a photon) is described by an element of a mathematical object called a Hilbert space.
		Qubits for a quantum computer can be implemented using particles with two spin states: "up" and "down"; in fact any system, possessing an observable quantity A which is conserved under time evolution and such that A has at least two discrete and sufficiently spaced consecutive eigenvalues, is a suitable candidate for implementing a qubit.
	www.reference.com /browse/wiki/Quantum_computer (2819 words)

	Kane quantum computer: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-10-22)
		A quantum dot is a semiconductor crystal with a diameter of a few nanometers, also called a nanocrystal, that because of its small size behaves like a...
		Quantum teleportation is a technique discussed in quantum information science to transfer a quantum state to an arbitrarily distant location using an entangled...
		Quantum information science is a field of research at the interface of quantum mechanics and computer science....
	www.absoluteastronomy.com /encyclopedia/k/ka/kane_quantum_computer.htm (1231 words)

	Quantum computer - Hutchinson encyclopedia article about Quantum computer
		In 1985, David Deutsch of the University of Oxford described a ‘universal quantum computer’ that would be able to perform feats beyond the capabilities of conventional computers.
		No such computer has been built to date, but quantum computing is thought to show great promise in certain areas, such as cryptography.
		Quantum particles obey the laws of quantum mechanics, which are different from the laws of classical physics.
	encyclopedia.farlex.com /Quantum+computer (212 words)

	Kane quantum computer - Wikipedia, the free encyclopedia
		The Kane quantum computer is a proposal for a scalable quantum computer proposed by Bruce Kane in 1998
		Often thought of as a hybrid between quantum dot and NMR quantum computers, the Kane computer is based on an array of individual phosphorus donor atoms embedded in a pure silicon lattice.
		Unlike many quantum computation schemes, the Kane quantum computer is in principle scalable to an arbitrary number of qubits.
	en.wikipedia.org /wiki/Kane_quantum_computer (582 words)

	IBM Research \| Press Resources \| IBM-Led Team Unveils Most-Advanced Quantum Computer
		Quantum computers get their power by taking advantage of certain quantum physics properties of atoms or nuclei that allow them to work together as quantum bits, or "qubits," to be the computer's processor and memory.
		While this is a necessary condition for achieving a quantum computer, they have not yet used the molecule as a seven-qubit quantum computer to solve a problem or to implement a quantum algorithm.
		To input and read the data in a quantum computer, Chuang's team uses a nuclear magnetic resonance machine, which uses a giant magnet and is similar to the medical devices commonly used to image human soft tissues.
	domino.research.ibm.com /comm/pr.nsf/pages/news.20000815_quantum.html (1092 words)

	An introduction to Quantum Computing (Site not responding. Last check: 2007-10-22)
		Where a classical computer obeys the well understood laws of classical physics, a quantum computer is a device that harnesses physical phenomenon unique to quantum mechanics (especially quantum interference) to realize a fundamentally new mode of information processing.
		The simulation of a quantum computer on a classical one is a computationally hard problem because the correlations among quantum bits are qualitatively different from correlations among classical bits, as first explained by John Bell.
		The answer is primarily those errors that arise as a direct result of decoherence, or the tendency of a quantum computer to decay from a given quantum state into an incoherent state as it interacts, or entangles, with the state of the environment.
	www.cs.caltech.edu /~westside/quantum-intro.html (3038 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		This is the problem of decoherence and is a stumbling block for quantum computers as the potential power of quantum computers depends on the quantum parallelism brought about by the coherent state [14].
		Such a computer could be built from the quantum equivalent of the Toffoli gate and by adding a few extra operations that can bring about linear superpositions of 0 and 1 states, the universal quantum computer is complete.
		A quantum computer would, for example, allow the "Hubbard Model" (which describes the movement of electrons within a crystal) to be simulated, a task that is beyond the scope of current conventional computers.
	wwwhomes.doc.ic.ac.uk /~nd/surprise_97/journal/vol4/spb3 (5889 words)

	Quantum computer at opensource encyclopedia (Site not responding. Last check: 2007-10-22)
		A quantum computer is a device that computes using superpositions and entanglement of quantum states.
		Quantum computers are different from classical computers such as DNA computers and computers based on transistors, even though these use quantum mechanical effects other than state superpositions or entanglement.
		Some computing architectures such as optical computers may use classical superposition of electromagnetic waves, but without the uniquely quantum mechanical phenomenon of entanglement, they do not share the potential to exponentially accelerate certain calculations.
	www.wiki.tatet.com /Quantum_computer.html (2459 words)

	Parallel Power
		A quantum computer's central processor, its Pentium chip, could conceivably be nothing more than a beaker of some suitable liquid, whose molecules would include a variety of atomic spin states specially chosen to perform a set task.
		Flip a coin in the quantum realm and the outcome won't be heads or tails.
		For this reason, scientists expect that quantum computers will be able to use entirely new algorithms to solve a variety of problems more efficiently than conventional machines.
	members.fortunecity.com /templarser/qcomp1.html (2218 words)

	IBM Research \| Press Resources \| IBM's Test-Tube Quantum Computer Makes History
		A quantum computer gets its power by taking advantage of certain quantum properties of atoms or nuclei that allow them to work together as quantum bits, or "qubits," which serve simultaneously as the computer's processor and memory.
		While the potential for quantum computing is huge and recent progress is encouraging, commercial quantum computers are still many years away.
		The first quantum computing applications would likely to be co-processors for specific functions, such as solving difficult mathematical problems, modeling quantum systems and performing unstructured searches.
	domino.research.ibm.com /comm/pr.nsf/pages/news.20011219_quantum.html (921 words)

	ScienceDaily: Lucent Technologies Researcher Shows Quantum Computers Can Perform More Applications Than Previously ...
		While digital computers rely on transistors switching on and off to perform its tasks - the switch is either a 1 or a 0 - the processing units in quantum computers could simultaneously register a 0 and 1.
		Quantum computer -- A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on...
		Quantum entanglement -- Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be...
	www.sciencedaily.com /releases/1998/05/980522151024.htm (2000 words)

	Howstuffworks "How does a quantum computer work?"
		According to quantum physics, a subatomic particle can't be absolutely said to exist: It exhibits a statistical probability to exist in a particular place and time, but there's no way of knowing whether it's there or not until you observe it, at which point all the probabilities collapse down into a definite state.
		Researchers at IBM have built quantum computers by using nuclear magnetic resonance (NMR) techniques to measure and manipulate the spin of individual atoms.
		Radio-frequency energy bursts can begin the "computing" process by changing the energy level of an atom, which might then interact with other atoms in a controlled manner, to establish the patterns of quantum computing that correspond to answers that might be gathered through normal computers.
	www.howstuffworks.com /question475.htm (597 words)

	Quantum computer solves problem, without running
		Using an optical-based quantum computer, a research team led by physicist Paul Kwiat has presented the first demonstration of "counterfactual computation," inferring information about an answer, even though the computer did not run.
		While the researchers' optical quantum computer cannot be scaled up, using these kinds of interrogation techniques may make it possible to reduce errors in quantum computing, Kwiat said.
		With computers getting faster, and faster, and smaller and smaller, and cheaper and cheaper, if you plot this trend on a graph, eventually we will be able to do everything with nothing..and it will be free.
	www.physorg.com /news11087.html (860 words)

	BBC NEWS \| Science/Nature \| Quantum computer draws closer
		He believed there was something profound in the phenomenon and that buried in its seeming absurdity lay something that could overthrow quantum mechanics - a successful theory of the way the Universe behaves on the atomic and sub-atomic level.
		Today's computers are limited by the speed of electrons as they move around integrated circuits.
		According to some, a computer based on quantum entanglement would not be bound by those limits as it would use "spooky action at a distance" instead of electrons or photons.
	news.bbc.co.uk /1/hi/sci/tech/3043731.stm (558 words)

	Wired News: Quantum Leap in Computing
		Still, quantum computers may never be general-purpose computing devices and are more likely to be targeted at massive number-crunching problems like encryption and decryption, searches of huge databases and simulations of quantum physical states.
		Laflamme's quantum computer was created by manipulating the nuclei of seven molecules in a test tube of trans-crotonic acid, hence 7-qubit.
		Wineland is working on one of several different approaches to quantum computing that utilizes trapped ions instead of fluid liquids.
	www.wired.com /news/technology/0,1282,35121,00.html (731 words)

	Bulk Spin Resonance Quantum Computation (Site not responding. Last check: 2007-10-22)
		Quantum computation is an exciting prospect, because a quantum computer (if it could be built) would be exponentially faster than a classical computer on some problems.
		For example, a quantum computer could find prime factors in polynomial time instead of the exponential time required by a classical computer, thereby breaking conventional cryptographic codes.
		The problem with building a quantum computer is that the quantum bits (called qubits) simultaneously need to be protected from the environment so that they retain their quantum phase, but they need to be coupled to the environment so that initial conditions can be loaded, the calculation applied, and the results read out.
	www.media.mit.edu /physics/projects/spins (530 words)

	Physics 219 Course Information
		Quantum Computation and Quantum Information by Michael Nielsen and Isaac Chuang, will be available in the fall of 2000.
		And a quantum computer -- a new type of machine that exploits the quantum properties of information -- could perform certain types of calculations far more efficiently than any foreseeable classical computer.
		A quantum computer will be much more vulnerable than a conventional digital computer to the effects of noise and of imperfections in the machine.
	theory.caltech.edu /people/preskill/ph229 (1043 words)

	Quantum computation: a tutorial
		Imagine a computer whose memory is exponentially larger than its apparent physical size; a computer that can manipulate an exponential set of inputs simultaneously; a computer that computes in the twilight zone of Hilbert space.
		A schematic model of a quantum computer is described as well as some of the subtleties in its programming.
		The Shor algorithm [1,2] for efficiently factoring numbers on a quantum computer is presented in two parts: the quantum procedure within the algorithm and the classical algorithm that calls the quantum procedure.
	www-users.cs.york.ac.uk /~schmuel/comp/comp.html (615 words)

	Walther Group: Quantum Computer (Site not responding. Last check: 2007-10-22)
		In recent years it was recognized that by exploiting the laws of quantum mechanics, information may be processed in a far more effective way than on a purely classical basis.
		A system particularly well suited for quantum computing is a chain of ions in a linear ion trap.
		Quantum bits may be stored, for example, in two hyperfine ground states of each ion, while quantum logic transformations can be realized using the coupling provided by the quantized vibrational modes of the ions.
	www.mpq.mpg.de /QuantumComputer.html (200 words)

	NIST: Physics Laboratory's - Quantum Information
		The starting point for quantum information at NIST was in 1995 when the Ion Storage Group demonstrated the first quantum-logic gate.
		Quantum Computers May Be Easier to Build Than Predicted, NIST Work Suggests.
		The figure shows memory qubits in a quantum register and an accumulator where the qubits in the quantum register can be moved together to undergo quantum operations.
	qubit.nist.gov (1015 words)

	Technorati Tag: quantum computer (Site not responding. Last check: 2007-10-22)
		Quantum Computers at Shopping.com Find, compare and buy products in categories ranging from hard drives to tape drives.
		Quantum Computer Find Deals on Quantum Computer and other Computer Storage Products at DealTime.
		Researchers develop a quantum nano-mechanical system that could measure the spin of a single...
	technorati.com /tag/quantum+computer (514 words)

	University of Michigan develops quantum processor \| TG Daily (Site not responding. Last check: 2007-10-22)
		Quantum computing has been touted as great leap in computing, but still faces many challenges.
		A traditional computer would do everything in series, meaning multiply one by one, but a quantum computer has already calculated all the answers.
		Quantum computers can excel in computations involving waveform analysis or cryptography or anything where you must reduce a large set of data to find an answer, but don't do as well with Microsoft Word or checking email.
	www.tgdaily.com /2006/01/17/uofmich_quantumchip (768 words)

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