Researchers untangle vital problem in quantum computing

Washington, June 12 : Two researchers from Arizona State University in the US have untangled a vital problem in quantum computing, which could help in the realization of next generation computers.

Quantum computing has been hailed as the next leap forward for computers, promising to catapult memory capacity and processing speeds well beyond current limits.

But, several challenging problems need to be cracked before the dream can be fully realized.

Now, Richard Akis and Professor David Ferry, both of the electrical engineering department's Nanostructures Research Group at the Arizona State University, have proposed a solution to one of the most controversial of these conundrums and, in the process, may have taken a significant step toward realizing a quantum computing future.

Two basic requirements of any computer are the capacity to store a value (information) and the ability to read that value. Yet even these most basic requirements present cutting-edge challenges to quantum physicists.

Today's computers store data logically as bits-ones and zeroes represented physically as positive or negative charges in a storage medium.

Quantum computers, conversely, will store data logically as quantum bits, or "qubits"-an entire range of values represented physically by an electron's angle of spin.

Electrons and other subatomic particles spin like tiny tops, complete with tilt, or "precession."

Since there are an infinite number of angles at which an electron can tilt, there are theoretically an infinite number of values that a qubit can store. Practically speaking, however, the number of available values will be constrained by technology and other theoretical limitations of computer science.

Currently, researchers are hard pressed to build even simple quantum computers. The problem is that quantum states are notoriously difficult to pin down and measure.

Akis and Ferry's research combined with that of former ASU colleague Jonathan Bird, could yield insights that help solve these problems.

Bird, now at University of Buffalo, has made important strides toward measuring quantum states using "entanglement," a characteristic of quantum mechanics by which two quantum particles interact at a distance.

His measurement technique is based on quantum states produced by electron-electron interactions.

Bird's method is only useful, however, if it has something to measure and a theory to back it up, but electron-electron interactions are complex and poorly understood. kis and Ferry were wrestling with one of the most controversial of these questions when they came up with a model that explained the electron-electron interactions Bird was measuring.

"Bird's experiment is more than a pretty measurement-there are indications that you could use this in quantum computing applications," said Ferry.

Their findings could also have important implications for quantum data storage.

ANI