Hideo Kaiju: The Challenge of Fusion Research

2024/08/28

It is said that we have now 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 contracts worldwide reached approximately 8.5 billion in 2023, and the amount of data information 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 approximately 10 to the 23rd power. At first glance, this seems like an astronomical figure, but from the perspective of those of us specializing in condensed matter physics, it does not seem that large. One cubic centimeter of matter contains approximately 10 to the 23rd power of electrons. In other words, if information could be recorded on each of these electrons, all the digital data currently on Earth could be stored in a small substance of just one cubic centimeter.

In recent years, methods using electron spin have been proposed as a way to record information 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. Spintronics is the new field we are pioneering, which "fuses" such spin with electronics, one of the foundational technologies of modern information.

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 are aligned, 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 components are interesting, new discoveries will not be born unless they are fused effectively. Conversely, when they fuse well, great discoveries are made, sometimes leading to the birth of new interdisciplinary fields. I believe the same is true for compatibility between people, or the harmony between one's own mind and body.

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