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Hideo Kaiju: The Challenge of Fusion Research

Publish: August 28, 2024

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  • Hideo Kaiju

    Faculty of Science and Technology Professor, Department of Applied Physics and Physico-Informatics

    Specialization / Magnetic Physics, Spintronics

    Hideo Kaiju

    Faculty of Science and Technology Professor, Department of Applied Physics and Physico-Informatics

    Specialization / Magnetic Physics, Spintronics

It is said that we have entered the era of the information explosion. According to the recently released "State of World Population 2024," the latest world population in 2024 has exceeded 8.1 billion. The cumulative number of smartphone and mobile phone subscriptions worldwide reached approximately 8.5 billion in 2023, and the amount of data used globally is predicted to reach 180 zettabytes by 2025.

"Zetta" is a billion times a trillion, representing 10 to the 21st power. In other words, 180 zettabytes is roughly 10 to the 23rd power. At first glance, this seems like an astronomical figure, but from the perspective of those of us specializing in physical properties, it does not seem that large. This is because one cubic centimeter of matter contains approximately 10 to the 23rd power of electrons. In other words, if information could be recorded on each individual electron, all the digital data currently on Earth could be stored in a small substance of just one cubic centimeter.

In recent years, a method using electron spin has been proposed as a way to record data on electrons. Electrons have a degree of freedom called "spin," which corresponds to rotational motion. This spin can be clockwise or counter-clockwise. In terms of magnets, these correspond to the North and South poles. The idea is to map these North and South poles to the "1" and "0" of digital data. The new field we are pioneering, which "fuses" such spin with electronics¡ªone of the foundations of modern information technology¡ªis spintronics.

What I want to convey here is not about spintronics itself, but the importance of "fusion." As is well known, electrons and light can be described as waves. Waves have not only amplitude but also phase. When phases align, for example in an electric circuit, resonance occurs. In the case of light, laser oscillation occurs. On the other hand, if the phases are even slightly out of alignment, these effects diminish and, in some cases, disappear. The same applies to research. Even if individual elements are interesting, new discoveries will not be born unless they fuse well. Conversely, when they fuse successfully, great discoveries are made, sometimes giving birth to new interdisciplinary fields. I believe the same applies to everything, including compatibility between people, or the harmony between one's own mind and body.

Aligning the phases is very important. I believe it is a necessary element for contributing to humanity and society and for enriching the world.

*Affiliations and titles are those at the time of publication.