[No. 55] Yutaka Yoshikawa

Although I am still an early-career researcher, having graduated from this university only about seven years ago, I have been given the opportunity to contribute to this website. I would like to thank everyone involved for this opportunity. I hope that through this article, readers can get a sense of the joy (and perhaps the rigor?) of a researcher's life.

After enrolling in the Faculty of Science and Technology at this university, I chose the Department of Physics and studied here for a total of six years until completing my master's program. I first became interested in physics and considered pursuing this field during high school. I remember being greatly intrigued by the principle of the constancy of the speed of light and Lorentz contraction while reading a popular science book on the theory of relativity. Because of this, I initially wanted to join a theoretical research laboratory when I entered university. However, in my third year as an undergraduate, in a class taught by Professor Hiroyuki Sasada, who would later become my supervisor, I learned about an experimental technique called "laser cooling," which uses lasers to cool matter to extremely low temperatures. At the time, my rudimentary understanding was that "low temperature" meant liquid helium, and the shock of having that notion shattered in an instant was immense. Fascinated by this technology, I was assigned to the Sasada Laboratory from my fourth year and began my journey as an experimentalist.

For three years until I completed my master's program, I was rigorously trained in various skills at the Sasada Laboratory. This included not only the fundamentals of quantum electronics (a field of study that investigates the properties of light itself and the interaction between light and matter, primarily using lasers; laser cooling is also part of this field) but also building electronic circuits with transistors and machining with lathes and milling machines. As I had loved making things since childhood, the task of building my own experimental apparatus was extremely enjoyable. From the second half of my second year in the master's program, I also participated in a joint research project on Bose-Einstein condensation of gas atoms (in simple terms, an atomic version of a laser) with Professor Takuya Hirano of the Department of Physics, Faculty of Science, Gakushuin University. After a grueling research period with only three hours of sleep per night, we finally obtained experimental results on New Year's Day 2001, and I managed to complete my master's thesis (something I definitely couldn't do now due to a lack of physical stamina). Those six months were the toughest period of my research life so far, but at the same time, it was a period when my skills as an experimentalist improved dramatically.

October 2, 2004, at the Uehara and Sasada Laboratories alumni reunion.

Afterward, I transferred to the Hirano Laboratory for the Doctoral Programs, but in less than a year, I was hired as a research associate (now assistant professor) in Professor Takahiro Kuga's laboratory at The University of Tokyo's Komaba Campus, and I took up the position in April 2002. The duties of an assistant professor involve managing and supervising laboratory experiments for first- and second-year undergraduate students, as well as assisting graduate students with their research. Naturally, my role expanded from just "research" to include "education." In the student labs at Komaba, a single faculty member sometimes has to supervise as many as 60 students a day. Although I am used to it now, when I first started, I struggled to manage everything and caused some trouble for the students. I have also recently come to realize that physics is an incredibly difficult subject to teach to students. It is easy to write down equations, but it is quite challenging to make them understand the physical meaning behind them. Even with relatively simple content like student experiments, I often find it difficult to get my point across, and I continue to go through a process of trial and error every day.

Finally, a little about my current research. Although there have been some changes compared to the past, the core of my research theme is still laser cooling. It is strange that I am still attached to this topic, even though it caused me so much trouble during my student days. As a student, all I could do was diligently tackle the tasks given to me by my professors one by one. Recently, however, I have finally become able to find my own research themes, build experimental apparatus, analyze the results, and present them in papers and at academic conferences. All of this is possible because of the intensive research experience I had while at Keio. I am deeply grateful to the professors who have guided me.

This year marks my 10th year as an experimentalist. The catalyst was a brief, 10-minute digression in Professor Sasada's lecture during my third year of undergraduate studies. You truly never know when a turning point will come.