New circuits feed on noise

Digital circuits turn buzzing environments into an advantage

Teenagers swear they study better with music blaring in the background, though parents may disagree. Now engineers have made digital circuits work better in “noisy” environments too.

For circuits, the noise isn’t the sound of the latest Top 40, but a background buzz that normally disrupts computer processing. Researchers report in the March 13 Physical Review Letters that they have designed new digital circuits that not only cope with this buzz, but need it to work properly.

The work is “very cool, because it takes the inherent noise in a system and puts it to good use,” comments physicist Raj Mohanty of Boston University.

As engineers design smaller computer chips, noise from electronic component cross talk, electrons moving around and a variety of other sources becomes a bigger problem. “You can imagine that 10 electrons moving around something as big as your arm isn’t a big deal. But 10 electrons moving around something as small as an atom is a big deal,” says engineer and study coauthor William Ditto of Arizona State University in Tempe. “Computers can’t get any smaller or faster unless we do something different,” he adds.

One type of circuit, called a nonlinear circuit, needs noisy conditions to work. Nonlinear circuits work with noise by using stochastic resonance, a phenomenon that allows a small signal to combine with background noise to produce an output.

But nonlinear circuits work in a random, chaotic way and don’t produce the logical outputs that computer systems are built around. Ditto and his colleagues figured out how to make nonlinear circuits produce outputs in the same orderly fashion as traditional computer circuits, providing a possible alternative to circuits that can’t work in too much noise. What’s more, the new nonlinear circuits can adapt to the amount of noise in a system.

Exactly how the nonlinear systems are able to turn noisy environments into an advantage remains unclear. “We’re not sure exactly how nonlinearity and noise combine in these systems,” Ditto says. But the new circuits could make devices “smaller, more reliable, faster and cheaper.”

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