Monday July 4, 06:00 PM By Will Knight An exotic light-wielding computer that should be capable of immensely complex calculations has been designed by a team of British and Japanese researchers. Bill Munro and Tim Spiller at Hewlett-Packard's research laboratory in Bristol, UK, and Kae Nemoto from the National Institute for Informatics in Tokyo, Japan, devised the quantum computer, which will control single photons of light using powerful laser pulses in order to process quantum bits - or qubits - of information. Computers that perform calculations by harnessing the bizarre properties of quantum physics - such as the superposition or entanglement of particles - could one day operate at extraordinary speeds. Quantum computers should, for example, be able to perform multiple calculations at once simply by exploiting the fact that quantum particles can simultaneously occupy two distinct states. There are numerous competing schemes for building quantum computers and several research groups have succeeded in building very simple quantum calculating devices. The most popular method for quantum computing involves controlling charged atomic particles with electromagnetic fields. Previous designs incorporating particles of light have proven notoriously unstable, but the team say their photon-based device should be far more robust and scalable. The system would use laser beams as a communication channel between optical qubits. Information on the quantum state of qubits would be combined in the beam, and then processed by measuring the beam. This would make it much less difficult to process quantum information, as beams can be controlled more easily than single particles of light. The researchers calculate that the scheme could be used to fashion a fundamental computing component known as a logic gate. Stringing several of these together would then yield more complex components. "It's a very exciting idea," says Konrad Banaszek at Nicolaus Copernicus University in Poland, who has worked on other designs for photon-based quantum computers. Banaszek adds that a detailed experimental analysis of the design is crucial. But he says it is "quite clear" the new design will operate differently and more efficiently that other designs of optical quantum computers. Photons can also be used to transmit information between computers, and Spiller says the design could also be used to link quantum computing to light-based communications systems. "In principle, this could work as a marriage of the two," he told New Scientist . The formidable processing power of a fully-fledged quantum computer would fundamentally change the computer industry. It would also immediately undermine the encryption codes currently used to secure online communications and transactions, as these are based on the complexity of certain mathematical problems. However, quantum encryption could help fill that need. Journal reference: New Journal of Physics (vol 7, article 137) Related Stories from New Scientist: Quantum computer springs a leak 'Quantum well' transistor promises lean computing Quantum tricks that read your thoughts Click here to visit the New Scientist website Article Preview Quantum tricks that read your thoughts 04 December 2004 Mark Buchanan Magazine issue 2476 The weird world of quantum entanglement This could change the way the world does business, says Mark Buchanan IT IS the weirdest of the weird - Einstein certainly had no time for it. So how come quantum entanglement is being touted as the solution to some of humanity's most pressing issues? Entanglement is the bizarre phenomenon of quantum particles such as electrons remaining mysteriously linked, even when separated by enormous distances. Do something to one, and something happens to the other instantly, as if they weren't really separate at all. Einstein doubted its existence, yet today physicists are putting it to work to build super-fast quantum computers and unbreakable quantum codes. And now researchers are considering a very strange use: pseudo-telepathy. That may sound frivolous, but it could have profound impact - helping humanity to solve age-old dilemmas. For half a century, economists and evolutionary biologists have relied on "game theory" to make sense of a wide range of competitive situations, from ecosystems to international politics. The theory ... The complete article is 2344 words long. Quantum computer springs a leak 26 June 2005 NewScientist.com news service Mark Buchanan ATTEMPTS to build quantum computers could run up against a fundamental limit on how long useful information can persist inside them. Exceed the limit and information could just leak away, making computation impossible. "Quantum information will inevitably be lost after a certain time, even without any external disturbance"A quantum computer manipulates stored information in quantum bits, or qubits. Because a qubit can be in twostates at the same time, and can be entangled with other qubits, a quantum computer can carry out multiple calculations simultaneously. But the entire system is delicate: during a computation the qubits have to be isolated from their environment, because any outside disturbance can cause "decoherence" and spoil the calculations. Coherence is harder to maintain in larger qubits containing more particles, because there is more potential for interaction with the surroundings. To try and limit this effect, researchers are pursuing ways of making microscopic qubits. These can be made using superconducting circuits on silicon chips or with quantum dots, which are essentially droplets of semiconducting materials that contain free electrons. In principle, qubits can be made out of individual electrons and photons. But physicists Jasper van Wezel, Jeroen van den Brink and Jan Zaanen of Leiden University in the Netherlands have shown that efforts to engineer quantum computers around ever-smaller qubits may face significant obstacles. "We have proven that there is a universal decoherence rate for qubits," says van den Brink. This means that quantum information will inevitably be lost after a certain time, even without any external disturbance. Rather than remaining in a superposition of two states, a qubit will spontaneously collapse into one state or another (Physical Review Letters, vol 94, p 230401). "When we discovered this we were stunned," says van den Brink. Worryingly, the time limit for decoherence seems to grow shorter as systems get smaller. Zaanen says that for some of the most promising qubit technologies the limit would be about 1 second. It's not a problem at the moment, he says, because researchers are fighting to get coherence times up to around a microsecond. "But this fundamental limit is getting within reach." "This is very interesting," says physicist Peter Zoller of the University of Innsbruck in Austria. But the real implications for quantum computing will only become clear with further work, especially experiments that would measure these effects, he says. Related Articles Quantum chips may work above absolute zero 23 April 2005 'Quantum well' transistor promises lean computing 10 February 2005 Stopping light gives atoms a memory 15 January 2005 Search New Scientist Contact us Web Links Leiden Institute of Physics Peter Zoller, University of Innsbruck Physical Review Letters From issue 2505 of New Scientist magazine, 26 June 2005, page 18 -------------------------------------------------------------------------------- Researchers Develop Quantum Processor Jay Wrolstad, newsfactor.com Fri Jan 13, 4:50 PM ET A computer chip based on the esoteric science of quantum mechanics has been created by researchers at the University of Michigan. The chip might well pave the way for a new generation of supercomputers. Employing the same semiconductor-fabrication techniques used to create common computer chips, the Michigan team was able to trap a single atom within an integrated chip and control it using electrical signals. Two Places at Once As of yet, the technology is not applicable to typical desktop PCs or servers, but quantum computers are said to be promising because they can solve complicated problems using massively parallel computing. That is accomplished by the quirky nature of quantum mechanics, said Christopher Monroe, a physics professor and the principal investigator and co-author of the paper "Ion Trap in a Semiconductor Chip." He explained that that chips can process multiple inputs at the same time in the same device. "With quantum mechanics, an object can be in two places at the same time, as long as you don't look at it," he said. The quantum computer architecture can store quantum bits (qubits) of information, where each qubit can hold the numbers one or zero, or even both digits simultaneously. When a qubit is added to a quantum system, the computing power doubles. Thus, the quantum machine can crunch numbers at a rate that is exponentially faster than conventional processors, said Monroe. New Spin on Semiconductors Electrically charged atoms (ions) for such quantum computers are stored in traps in order to isolate the qubits, a process that is essential for the system to work. The challenge is that current ion traps can hold only a few atoms, or qubits, and are not easily scaled, making it difficult to create a quantum chip that can store thousands or more atomic ions. A string of such atoms, in theory, could store thousands of bits of information. In the chip created at Michigan, which is the size of a postage stamp, the ion is confined in a trap while electric fields are applied. Laser light puts a spin on the ion's free electron, enabling it to flip it between the one or zero quantum states. The spin of the electron dictates the value of the qubit. For example, an up-spin can represent a one, or a down-spin can represent a zero -- or the qubit can occupy both states simultaneously. Applications for Cryptography The quantum processor is made of gallium arsenide in a layered structure and etched with electrodes using the same type of lithography process as those used to create today's computer chips. Each electrode is connected to a separate voltage supply, and these various electrical voltages control the ion by moving as it hovers in a space carved out of the chip. The next step is to build a bigger chip with many more electrodes, so that it can store more ions. There still is a lot of work to be done to learn how to control lots of ions in one of these chips. It won't be nearly as easy as it was with conventional computer chips, but at least we know what to do in principle, Monroe said. "This type of integrated chip structure is significant because it demonstrates a way to scale the quantum computer to bigger systems," Monroe said. "It has applications for processing very large [data sets] such as in cryptography, for example, and there is a lot of interest in this by the government." Copyright © 2006 Yahoo! Inc. All rights reserved.