Quantum computing, which holds the promise of nearly unlimited processing power and secure communications, is a significant step closer to becoming a reality with research published by a team of UCLA scientists.

The UCLA scientists succeeded in flipping a single electron spin upside down in an ordinary commercial transistor chip, and detected that the current changes when the electron flips. Their report of controlling and detecting a single electron's spin was published in the journal Nature.

Scientists had manipulated millions of electron spins in a transistor before, but never a single electron.

"We have gone from millions to just one," said HongWen Jiang, a UCLA professor of physics and member of the California NanoSystems Institute, in whose laboratory the experiments were conducted.

"Our research demonstrates that an ordinary transistor, the kind used in a desktop PC or cell phone, can be adapted for practical quantum computing," Jiang said. "The research makes quantum computing closer and more practical."

A single electron spin represents a quantum bit, the fundamental building block of a quantum computer.

Many scientists believe that an exotic new technology would be required for quantum computing. However, Jiang said, "I would not be surprised one day to see a quantum computer built, based almost entirely on silicon technology."

"We have measured a single electron spin in an ordinary transistor; this means that conventional silicon technology is adaptable enough, and powerful enough, to accommodate the future electronic requirements of new technologies like quantum computing, which will depend on spin," said Eli Yablonovitch, UCLA professor of electrical engineering, director of UCLA's Center for Nanoscience Innovation for Defense, member of the California NanoSystems Institute and co-author of the study. "We've done this with a commercial silicon integrated circuit chip, literally off a shelf."

How powerful can quantum computing be?

"With 100 transistors, each containing one of these electrons, you could have the implicit information storage that corresponds to all of the hard disks made in the world this year, multiplied by the number of years the universe has been around," Yablonovitch said. "And why stop with 100 transistors? We've manipulated one spin. A year from now, manipulating a single spin might be all in a day's work, and in 10 years, perhaps it will have a commercial role."

If manipulating a single electron's spin will soon seem routine, until now it has been anything but. Jiang and his UCLA graduate student Ming Xiao worked day and night to achieve this goal, and thought about quitting more than once.

"There were so many unknowns," Jiang said, "but our initial theoretical calculations were very favorable, and gave us confidence to persevere."

Jiang and Xiao succeeded in working with the transistor at low temperatures: minus more than 400 degrees Fahrenheit. Jiang and Yablonovitch have ideas for operating in the future at room temperature, which would be much more practical commercially.

Jiang and Xiao's method for controlling the electron was to shine a microwave radio frequency to flip the spin of the electron. The experiments last but a fraction of a second, but required years of work to reach this point.

Electrons rotate like spinning tops. The UCLA team can target a single electron and control when it is right side up and when it is upside down by changing the microwave frequency.

A next step is to demonstrate the "entanglement" of two spins, where the orientation of one electron determines the orientation of the other--a puzzle identified by Albert Einstein.

The research, a combination of physics and engineering, was funded by the United States Defense Advanced Research Projects Agency, the United States Defense MicroElectronics Activity and the Center for Nanoscience Innovation for Defense.