Shining a new light on electron spin
by Ted Smalley Bowen, Technology Research NewsResearchers are beginning to get a handle on how to build phenomenally powerful quantum processors, but figuring out how to shuttle data in and out of them is a major obstacle to making quantum computers practical.
University of Toronto researchers propose to solve the problem by using laser pulses to move electrons without introducing an electrical charge.
Because particles like electrons spin in one of two directions, the spin directions can represent the ones and zeros of binary computing. "The method allows us to sort electrons by their spin," said John Sipe, a physics professor at the University of Toronto.
Using light to control the flow of electrons could foster new data processing and data storage methods, as well as point the way to solid-state quantum computers.
Other researchers have preserved the spins of electrons while moving them the standard way using charge, and several research teams have demonstrated spin-based transistors that could eventually yield ultralow-power processors and high-density data storage devices.
However, it would be extremely difficult to use charge to move electrons in quantum computers because quantum processors are extremely fragile and need to be insulated from their environments.
"People have suggested doing quantum computing with spins in solids, and our technique could be an important tool in moving spins around for information processing or read-in and read-out," said Sipe.
The Toronto researchers propose generating electron spin currents in semiconductors using the interference between two colors of light. The electrical currents could be controlled by adjusting the relative phase, or difference in wavelengths, of the two beams, according to the researchers. In this scheme, the interference would sort the electrons, sending those of one spin in one direction and those of the opposite spin in the opposite direction.
"Their idea is an exciting addition to the rapidly expanding collection of tools for optical manipulation of spin in solid state systems," said Jay Kikkawa, assistant professor of physics and astronomy at the University of Pennsylvania.
Sipe's research colleague was Ravi Bhat. The two published their work in the December 18, 2000 issue of Physical Review Letters. It was funded by the Ontario government's Photonics Research Ontario program and the Canadian government's National Sciences and Engineering Research Council.
Timeline: Unknown
Funding: Government
TRN Categories: Semiconductors, Quantum Computing
Story Type: News
Related Elements: Technical paper, “Optically Injected Spin Currents in Semiconductors,” Physical Review Letters, December 18, 2000
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January 3, 2001
Page One
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Security comes one photon at a time
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