Utilizing Every Possible Method to Challenge the Ultimate Goal
Masazumi Honda
(Senior Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) / Visiting Professor, Graduate School of Science and Engineering, Saitama University)
What are the fundamental building blocks of the universe? What is the ultimate physical law that govern the universe? How did the universe begin? Theoretical high energy physics, which seeks to answer these profound questions, is the main research field for Masazumi Honda. We spoke with Honda about his journey to iTHEMS, the breadth of his research approaches and disciplines, and his recent research on applying quantum computers to high energy physics.
Keywords: Theoretical Physics, High Energy Physics, Quantum Computing, Condensed Matter Physics, Postdoc
Affiliation and position are as of the interview date: December 2024
Current position: Senior Research Scientist, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)
(Written by Shino Suzuki (Photon Create Co., Ltd.) / Photographed by Makoto Oikawa (Photographer))
An Ideal Environment for My Current Research Phase
"iTHEMS brings together researchers from a wide array of fields, making it an unparalleled environment worldwide and the best place for me right now." Honda thinks that the optimal research environment changes depending on the phase of a researcher's career. "As a student or postdoc, it would be beneficial to have many researchers in the same field around you for collaboration. However, as you gain experience and take a leading role in research, being surrounded by researchers from different fields can be an advantage."
After obtaining his Ph.D. in 2013, Honda conducted postdoctoral research in India, Israel, and the UK before returning to Japan, where he worked as an assistant professor at Yukawa Institute for Theoretical Physics in Kyoto University. Now, as a senior research scientist at iTHEMS, he has entered a phase where he takes a leading role in his research area.
Someone might wonder, “India? And then Israel?” Honda also says, "The fact that I have conducted postdoc research in various countries is a characteristic of my career." Let’s take a look at his path to iTHEMS.
Pursuing a Grand Purpose Without Restricting Methods
Theoretical high energy physics is a branch of physics, but Honda didn’t initially set out on this path. "When I entered undergraduate university, I was torn between studying physics and earth sciences." In high school, he became fascinated by methane hydrate—often called "flammable ice"—which exists in large quantities beneath the seabed around Japan, leading him to consider studying earth sciences at university. On the other hand, his strong interest in physics was sparked by a physics class at a preparatory school during his third year in high school.
"I thought most subjects, except for math, required a lot of memorization to score well. However, my physics teacher said that memorization should be minimal—just learning the fundamentals allows you to derive everything else. He also talked about unsolved mysteries and what kind of physics could be studied at university, making the classes incredibly enjoyable."
At the University of Tsukuba, students chose their major in the second year. After a year of broad exposure to natural sciences, Honda opted for physics. However, he almost had to repeat a year. "Most of us, including myself, lived alone near the university. It felt like a never-ending school trip, and I ended up playing too much," he laughs. "By my third year, I decided to pursue a career as a theoretical high energy physicist. Knowing that it was a highly competitive field with limited positions, I dedicated myself fully to physics from then on."
The goal of theoretical high energy physics is to unravel fundamental mysteries: What are the fundamental building blocks of the universe? What are the fundamental laws governing the universe? How did the universe begin? "It’s an overwhelmingly grand objective," says Honda. "Precisely because of this, I want to approach it without restricting my methods." He prefers long-term, fundamental research over flashy but transient studies—an approach that remains consistent throughout his career.
Choosing the Path Without Regret Even If Unsuccessful
During his final year in Ph.D. course, Honda applied to many postdoctoral positions in universities and research institutions worldwide. Among the offers he received, he chose the Harish-Chandra Research Institute in India. In that year, he spent three months visiting research institutions in India, Denmark, Germany, the U.S., and Brazil, with the first stop being the Harish-Chandra Research Institute.
According to Honda, exceptional researchers appear randomly worldwide, with larger populations increasing the probability of their emergence. "Theoretical physics doesn’t require experimental facilities; research can be done with just pen, paper, and a computer. When an outstanding researcher emerges, others gather around them, fostering a thriving research environment. The Harish-Chandra Research Institute was precisely such a place," he explains. However, living in India presented challenges, with temperatures soaring near 50°C and significant cultural and dietary differences.
After about two years in India, he moved to Weizmann Institute of Science in Israel, a hub for world-class theoretical physicists, where he enjoyed three years in an excellent research environment.
He then spent one and halfyear at the University of Cambridge—renowned for its long history and contributions to theoretical physics—before returning to Japan as an assistant professor at Yukawa Institute for Theretical Physics in Kyoto University. His postdoctoral period abroad lasted six and a half years. Reflecting on that time, Honda states, "It was tough due to the intense competition and short-term contracts with an uncertain future. At the same time, the freedom to live as I pleased was enjoyable. It was a mix of both feelings."
When asked whether he ever considered quitting theoretical particle physics, he immediately replied, "Never." Instead of choosing the seemingly safer path, he asked himself which option he would regret more. "I realized that even if I failed in high energy physics, I would be happier having pursued it than not. So, my commitment to this field never wavered, even when the future was uncertain."
Applying Quantum Computing to High Energy Physics
Honda's postdoc experiences broadened his research approach, particularly during his time in the UK. At a networking event between Japanese from the University of Cambridge and the University of Oxford, he got to know a research applying quantum computing to numerical problems inhigh energyphysics. "There are computational problems in high energy physics that classical computers struggle with. I began exploring whether quantum computers could overcome these limitations." While at Cambridge, he started research in this area, and upon returning to Japan, he pursued it more seriously.
Expanding his methods led to interdisciplinary connections, bringing him into contact with quantum information, condensed matter physics, mathematical physics, and astrophysics. "At iTHEMS, all these fields are represented, allowing for daily discussions. The research environment is even better than I had imagined."
Should We Just Wait for Development of Quantum Computing Hardware?
Honda is actively engaged in various research projects at iTHEMS, one of which focuses on applying quantum computing to numerical problems in high energy physics. RIKEN has numerous research labs developing quantum computers, providing an ideal environment for this work.
However, Honda recently started considering a new approach. "Quantum computers are difficult to build, and we don’t know how long it will take for high-performance quantum computers to be realized. Should we just wait? Instead, I’m exploring whether my expertise of high energy physics and condensed matter physics can help accelerate the development of quantum computing."
Passing on the Joy of Research to the Next Generation
Honda actively shares the joy of research with the public, including a lecture titled "Exploring the Origins of the Universe with Quantum Computers" at RIKEN Wako Open Day 2024. Since September 2024, he has also served as a visiting professor at Saitama University, emphasizing the importance of training the next generation. "The ultimate goal of particle physics is unlikely to be achieved within my lifetime. That’s why fostering future researchers is crucial."
"How did the universe begin? This is essentially the question of where we come from—a mystery pondered since ancient Greece, perhaps since the dawn of human consciousness. I’m truly glad I chose to pursue theoretical high energy physics."