WishX Posted July 31, 2002 Share Posted July 31, 2002 Tiny Device Traps Electrons for Quantum Computing By Jay Lyman NewsFactor Network July 29, 2002 A semiconductor-based device capable of trapping individual electrons and lining them up could bring quantum computing closer to reality, according to the University of Wisconsin researchers who designed it. The device ?- a single electron transistor -? serves as a source of electrons for tiny semiconductors known as quantum dots ?- which are about 50 billionths of a meter wide, UW professor of physics and project researcher Mark Eriksson told NewsFactor. In addition to quantum computing ?- which exploits electron spin to achieve the processing of exponentially more bits of information at the same time ?- the device may help in the creation of large databases as well as such data-intensive tasks as sophisticated encryption and code breaking, Eriksson said. Same as Semis The quantum dots designed at UW each contain a single electron and tiny amounts silicon-germanium -- the same semiconductor materials used in computer chips . "This material system is significant, because it is compatible with current silicon microelectronics," Eriksson said. When a number of the quantum dots are aligned, the electrons they house become usable bits, also known as qubits, which are the basis for quantum computing. Line 'Em Up Eriksson said the single electron transistor is unique, because it has a back gate directly beneath it, which serves as a source of electrons for the quantum dot. While he called the work "one piece of a very big picture," Eriksson said the quantum dots could supply the building block bits for quantum computing, which allows the processing of millions, or even billions, of bits of information at once. "The first prerequisite to building a large computer is to have a lot of bits, and we think we have a way to get a lot of them," Eriksson said. "We've done some sophisticated simulations with this device that show the concept is very likely to work, and we're in the beginning stages of actually making the device." Extreme Cold Required One limiting factor of the research is the requirement of cryogenic temperatures and a large magnetic field. "The requirement of cryogenic temperatures is a challenge, in the sense that it is very unlikely that each of us will have a low-temperature cryostat in our offices or homes," Eriksson said. "It is, however, conceivable that low temperatures will be tolerable for specialized applications." Eriksson said it is likely that any widespread use of quantum computing will require new advances to overcome this challenge. He expressed optimism on that score, though, noting that early computers required enormous rooms to function in, whereas they now can fit on desks or even in laps. Learning Tools, Toys The UW design is similar to a spintronic transistor built by the Institute for Microstructural Sciences in Ottawa, Canada. Andy Sachrajda, one of the scientists working on that project, told NewsFactor that the transistor also requires extreme temperature and a magnetic field, but it proves that spin-polarized leads can be used to determine the spin state of the electron and provides a way to explore quantum computing. "The ability to probe a controllable number of electrons down to one, with spin-polarized leads, is really a quite remarkable tool and toy for exploring this new field, and demonstrating new functionalities and principles," Sachrajda said. Quantum Convergence With a variety of pursuits that include atomic traps and superconductors, no one really knows what method or technology will produce the best quantum computer, according to Eriksson. However, he noted that the diversity of work and numerous, unanswered questions are what make the field so fascinating. "Challenges -- such as operating temperature -- are one reason that it is important that many different approaches to quantum computing be pursued simultaneously," Eriksson said. "They all have significant challenges, and it isn't yet clear which challenges will be easiest to overcome." Link to comment Share on other sites More sharing options...
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