Magnetic Computing Could Consume Far Less Power

Engineers at University of California, Berkeley, have confirmed for the first time that with magnetic chips, dramatic reductions in power consumption could be possible in computing.

The finding, rather a proof of a principle, known as Landauer limit, named after International Business Machine Corp. (IBM) Research Lab’s Rolf Landauer, suggests that magnetic computing can work at as little as one-millionth the amount of energy per operation used by transistors in modern computers.

Based on the laws of thermodynamics, Landauer found in 1961 that in any computer, each single bit operation must expend an absolute minimum amount of energy. He developed a formula and calculated the result: at room temperature, the lowest limit amounts to about 3 zeptojoules, or one-hundredth the energy given up by a single atom when it emits one photon of light.

In 2011, Jeffrey Bokor, a UC Berkeley professor of electrical engineering and computer sciences and a faculty scientist at the Lawrence Berkeley National Laboratory, and his team published a paper that said a memory bit could be manipulated and observed under conditions that would allow the Landauer limit to be reached.

In the new study, published in the latest issue of the peer-reviewed journal Science Advances, the team experimentally tested and confirmed the Landauer limit.

“We wanted to know how small we could shrink the amount of energy needed for computing,” explained Bokor, senior author of the study. “The biggest challenge in designing computers and, in fact, all our electronics today is reducing their energy consumption.”

“Making transistors go faster was requiring too much energy,” he said. “The chips were getting so hot they’d just melt.”

Researchers have been turning to alternatives to conventional transistors, which rely upon the movement of electrons to switch between 0s and 1s. Partly because of electrical resistance, it takes a fair amount of energy to ensure that the signal between the two states is clear and reliably distinguishable, resulting in excess heat.

Magnetic computing emerged as a promising candidate because the magnetic bits can be differentiated by direction, and it takes just as much energy to get the magnet to point left as it does to point right. “These are two equal energy states, so we don’t throw energy away creating a high and low energy,” said Bokor.

The UC Berkeley team used an innovative technique to measure the tiny amount of energy dissipation that resulted when they flipped a nanomagnetic bit, and used a laser probe to follow the direction that the magnet was pointing as an external magnetic field was used to rotate the magnet from “up” to “down” or vice versa.

They determined that it took 15 millielectron volts of energy, the equivalent of 3 zeptojoules, as calculated by Landauer, to flip a magnetic bit at room temperature.

Noting that putting magnetic chips into practical production will take more time, the researchers said in the paper that “the significance of this result is that today’s computers are far from the fundamental limit and that future dramatic reductions in power consumption are possible.” (PNA/Xinhua) JBP/EBP