A step closer to probabilistic calculus — ScienceDaily

Scientists at Tohoku University in Japan have developed a mathematical description of what happens in tiny magnets as they fluctuate between states when an electric current and a magnetic field are applied. Their findings, published in the journal Nature Communicationcould provide the basis for designing more advanced computers capable of quantifying uncertainty while interpreting complex data.

Conventional computers have brought us this far, but there are some problems they cannot effectively solve. Scientists have worked to solve this problem by designing computers that can use the laws of quantum physics to recognize patterns in complex problems. But these so-called quantum computers are still in their early stages of development and are extremely sensitive to their surroundings, requiring extremely low temperatures to operate.

Today, scientists are studying something different: a concept called probabilistic calculus. This type of computer, which could operate at room temperature, would be able to infer potential answers from complex inputs. A simplistic example of this type of problem would be inferring information about a person by examining their purchasing behavior. Instead of the computer providing a single discrete result, it selects patterns and provides a good estimate of what the result might be.

There could be many ways to build such a computer, but some scientists are investigating the use of devices called magnetic tunnel junctions. These consist of two layers of magnetic metal separated by an ultrathin insulator (Fig. 1). When these nanomagnetic devices are thermally activated under an electric current and a magnetic field, electrons pass through the insulating layer. Depending on their rotation, they can cause changes or fluctuations within the magnets. These fluctuations, called p-bits, which are the alternative to the on/off or 0/1 bits that we have all heard of in classical computers, could form the basis of probabilistic computation. But to design probabilistic computers, scientists must be able to describe the physics that occur in magnetic tunnel junctions.

This is precisely what Shun Kanai, a professor at Tohoku University’s Electrical Communication Research Institute, and his colleagues have realized.

“We have experimentally clarified the ‘switching exponent’ that governs the fluctuation under disturbances caused by magnetic field and spin transfer torque in magnetic tunnel junctions,” says Kanai. “This gives us the mathematical basis to implement magnetic tunnel junctions in the p-bit to design sophisticated probabilistic computers. Our work has also shown that these devices can be used to study unexplored physics related to thermally activated phenomena. “

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Material provided by Tohoku University. Note: Content may be edited for style and length.

Sherry J. Basler