Scientist registers leap in superfast quantum computing

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Princeton University's Jason Petta has demonstrated a method that alters the properties of a lone electron without disturbing the trillions of electrons in its surroundings.

The feat is likely to catalyse development of future varieties of ultra-fast computers with near-limitless capacities for data.

Petta, assistant professor of physics, has fashioned a new method of trapping one or two electrons in microscopic corrals created by applying voltages to minuscule electrodes.

Petta describes how electrons trapped in these corrals form "spin qubits," quantum versions of basic computer units known as bits, who conducted the research with Art Gossard and Hong Lu, University of California-Santa Barbara.

Previous experiments used a technique in which electrons in a sample were exposed to microwave radiation.

However, because it affected all the electrons uniformly, the technique could not be used to manipulate single electrons in spin qubits. It also was slow.

Petta's method not only achieves control of single electrons, but it does so extremely rapidly-- in one-billionth of a second.

"If you can take a small enough object like a single electron and isolate it well enough from external perturbations, then it will behave quantum mechanically for a long period of time," said Petta.

"All we want is for the electron to just sit there and do what we tell it to do. But the outside world is sort of poking at it, and that process... causes it to lose its quantum mechanical nature."

When the electrons in Petta's experiment are in what he calls their quantum state, they are "coherent," following rules that are radically different from the world seen by the naked eye.

Living for fractions of a second in the realm of quantum physics before they are rattled by external forces, the electrons obey a unique set of physical laws that govern the behaviour of ultra-small objects.

Scientists like Petta are working in a field known as quantum control which will help design quantum computers to take advantage of these characteristics to enrich their capacities in many ways, said a Princeton release.

However, long-term applications are still years away. "It's a one-day-at-a-time approach," Petta said.

These findings were published in Friday edition of Science.