I was deeply saddened to learn that Professor Anthony J. Leggett passed away on March 8.
Professor Leggett made pioneering contributions to our understanding of how quantum mechanics manifests itself in macroscopic matter. His theoretical work on superfluid helium-3 provided profound insights into quantum order in strongly interacting fermionic systems, and was recognized with the Nobel Prize in Physics in 2003. His work significantly advanced the study of quantum condensed matter and macroscopic quantum coherence.
In recent years, experiments using Josephson-junction circuits have demonstrated macroscopic quantum tunnelling and energy quantization in electrical circuits, developments that underpin modern superconducting quantum circuits and quantum computing. The Nobel Prize in Physics was awarded last year in recognition of these discoveries. In the official scientific background of that prize, Professor Leggett’s work is cited as an early theoretical proposal that Josephson junctions could provide a system in which quantum mechanics might be tested on a macroscopic scale. These developments can be understood as an experimental exploration of the question he posed about the quantum behavior of macroscopic physical systems.
Professor Leggett also provided warm support for researchers in Japan. His connection with Japan dates back to the 1960s. He spent about a year as a postdoctoral researcher in the Department of Physics, Kyoto University, where he lived in a student dormitory. During that time, he contributed an article to BUTSURI (Bulletin of the Physical Society of Japan) entitled “Notes on the Writing of Scientific English for Japanese Physicists,” which is still widely read by researchers in Japan today. In later years as well, he continued to value his exchanges with researchers in Japan, and his lecture at a colloquium held at RIKEN in 2018 also provided deep insights for many young researchers.
When my own team succeeded in observing excitonic Bose–Einstein condensation in 2022 after nearly two decades of effort, he kindly sent us a message of congratulations and encouragement.
In addition, during my tenure as President of the University of Tokyo, he generously supported the establishment of Tokyo College and served as its Honorary College Head.
I express my heartfelt gratitude for his kindness and extend my deepest condolences.
March 9, 2026
Makoto Gonokami
President, RIKEN