RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences

A New Principle for Controlling the “Butterfly Effect”

Takemasa Miyoshi (Team Principal, Data Assimilation Research Team, RIKEN Center for Computational Science (R-CCS) / Team Director, Prediction Science Research Team, Division of Applied Mathematical Science, RIKEN iTHEMS), has developed a new mathematical framework for efficiently controlling chaos by turning the fundamental limitation of predictability in deterministic chaos—widely known as the “butterfly effect”—to an advantage. He proposed a “duality principle,” demonstrating that data assimilation, which forms the foundation of weather forecasting (a process that synchronizes a model with the behavior of nature using observational data), and the control of chaos are mathematically twin concepts. Rather than suppressing chaos itself, this new approach exploits the high sensitivity characteristic of chaotic systems to synchronize real-world behavior with a manageable “target trajectory” through only a small amount of “intervention.” In this way, the study theoretically outlines a path toward controlling chaos beyond the conventional limits of predictability. This achievement provides a theoretical basis for future research in disaster prevention and mitigation—for example, applying minimal interventions to synchronize real atmospheric phenomena with a “typhoon scenario that causes no damage” (a target trajectory) simulated in a model, with the aim of avoiding extreme weather events. It is also expected to have applications in a wide range of fields that exhibit chaotic behavior, including ecosystems and economics. For further details, please refer to the related links.

2026-01-15

A 300-Billion-Particle Milky Way Simulation Achieved with AI × Fugaku

An international collaborative research team including Keiya Hirashima, Special Postdoctoral Researcher, has achieved the world’s highest-resolution simulation of the Milky Way galaxy by utilizing the entire system of the AI and supercomputer “Fugaku” (approximately 150,000 nodes) and modeling 300 billion particles representing stars, interstellar gas, and other components—resolving the galaxy down to individual stars. This research is expected to contribute to a better understanding of the Milky Way’s spiral arm structure (the arm-like features of spiral galaxies that extend outward from the center while winding across the galactic disk), the circulation of chemical elements within the galaxy, and the origins of the materials that formed the Solar System and life. For more details, please refer to the related links.

2026-01-15

RIKEN–IBS Joint Workshop on Mathematical Approaches to Nature Held in Daejeon, Korea, December 9–12, 2025

In December 9–12, 2025, a collaborative workshop jointly organized by the Institute of Basic Science (IBS, Korea) and RIKEN was held in Daejeon, Korea. The workshop aimed to explore the unifying mathematical principles that underlie diverse natural phenomena—from the fundamental interactions that shape the universe to the complex behaviors observed in living systems. From RIKEN, iTHEMS researchers including Derek Inman, Ryo Namba, Alvaro Pastor Gutierrez, Shuntaro Aoki, Sungsik Kong, Amaury Micheli, Puttarak Jai-akson, Ryoko Oishi-Tomiyasu, Che-Yu Chen, and Christy Kelly delivered talks. All the presentations were impressive and thoughtfully prepared so that researchers from different fields could follow and appreciate the content. Indeed, there were many stimulating cross-disciplinary questions, and we enjoyed lively discussions over lunches and dinners, accompanied by excellent (and wonderfully spicy) food. Although the workshop was originally designed to foster collaboration between RIKEN and IBS, connections were already present—for example, through Shuntaro Aoki, a physicist at iTHEMS formerly at IBS, and Shingo Gibo, a mathematical biologist at IBS formerly at iTHEMS. This workshop further strengthened these ties and created new ones. The planning and local organization of the workshop were led by the center of Masahide Yamaguchi (IBS), Yusuke Yamada (IBS), and by Yuto Yamamoto and Ryo Namba at RIKEN iTHEMS, with strong support from IBS and the International Collaboration Section of the Global Strategy Division at RIKEN. We are deeply grateful for their dedicated efforts. I hope that the successful interactions fostered through this workshop will continue to develop even further. (Photos: courtesy of Director Satoshi Iso, RIKEN iTHEMS.) Reported by Gen Kurosawa

2026-01-08

Yuya Kusuki Receives the 22nd (FY 2025) JSPS Prize

Yuya Kusuki (Visiting Scientist, iTHEMS / Associate Professor, Institute for Advanced Study, Kyushu University) has received the 22nd (Fiscal Year 2025) Japan Society for the Promotion of Science (JSPS) Prize. The JSPS Prize was established to recognize outstanding young researchers with exceptional creativity and research ability at an early stage of their careers, and to support their motivation and further development in research. Kusuki has made significant contributions through his research on the development and application of new methods at the interface between quantum gravity and quantum many-body systems. This award recognizes the originality and academic impact of his research achievements. The award ceremony is scheduled to be held on February 3, 2026, at the Japan Academy Hall. Congratulations, Yuya!

2026-01-06

Hokuto Konno receives the 22nd (FY 2025) JSPS Prize

Hokuto Konno (Visiting Scientist, iTHEMS / Associate Professor, the University of Tokyo) received the 22nd (FY 2025) Japan Society for the Promotion of Science (JSPS) Prize on December 16, 2025. The JSPS Prize was established to recognize outstanding young researchers with exceptional creativity and research ability at an early stage of their careers, and to support their motivation and further development in research. Konno was highly commended for his series of research achievements entitled “Family Gauge Theory and Its Applications to Four-Dimensional Topology.” This work elucidates deep connections between gauge theory and low-dimensional topology, and represents an important contribution to the theoretical development of mathematics. The award ceremony is scheduled to be held on February 3, 2026, at the Japan Academy Auditorium. Congratulations, Hokuto!

2025-12-23

Computing n-Time Correlation Functions without Ancilla Qubits

A research team led by Xiaoyang Wang (Postdoctoral Researcher, Quantum Mathematical Science Team, iTHEMS) has proposed a new method for computing n-time correlation functions, which play a central role in understanding the dynamics of quantum many-body systems. The proposed approach requires neither ancilla qubits nor controlled operations, and evaluates correlation functions using only the unitary time evolution of the system of interest. Conventional methods, such as the Hadamard test, rely on ancilla qubits that control the entire system, posing significant challenges for digital quantum processors with limited qubit connectivity and for analog quantum simulators where controlled operations are difficult or impossible to implement. The present work overcomes these limitations and broadens the range of quantum platforms on which multi-time correlation functions can be experimentally accessed. The protocol was demonstrated on IBM quantum hardware with up to 12 qubits, where the team successfully measured the single-particle spectrum of the Schwinger model and the out-of-time-order correlator (OTOC) in the transverse-field Ising model. In addition, an error-mitigation strategy based on signal processing—combining signal filtering and correlation analysis—was introduced, enabling the recovery of ideal noiseless simulation results from noisy experimental data. This work provides a new foundation for experimentally probing complex quantum many-body correlation functions under realistic hardware constraints, thereby strengthening the connection between theoretical predictions and quantum experiments.

2025-12-12

José Said Gutiérrez-Ortega receives the 19th Plant Species Biology Paper Award

José Said Gutiérrez-Ortega (Research Scientist, iTHEMS) has been selected as a recipient of the 19th Plant Species Biology Paper Award. The study analyzes the threats to the biocultural heritage of cycads in the Amami Islands through an international collaboration, including research conducted at RIKEN. The Plant Species Biology Paper Award is presented annually to 1–2 outstanding papers published in Plant Species Biology, selected by vote of the journal’s editorial board. The award was announced on 18 November 2025, and the award ceremony will be held on 20 December 2025 (Sat.) during the meeting of the Society for the Study of Species Biology. Congratulations, José!

2025-12-04

Tomoya Nagai receives the Poster Award at the 29th Interdisciplinary Exchange Evening

Tomoya Nagai (Coordinator, iTHEMS), together with Ayaka Shida (TRIP Promotion Office), Momoko Sato (IMS), and Hiroko Sakuma (Communications Division), has received the Poster Award at the 29th Interdisciplinary Exchange Evening. The Poster Award is presented to several outstanding contributions selected from among 59 poster presentations at this event, which aims to promote communication and collaboration among researchers from diverse fields. Each year, approximately five presentations are selected. The team’s poster investigated researchers’ attitudes and practices regarding the preparation of press releases. Their presentation attracted significant interest from both research and administrative staff within RIKEN. We would like to take this opportunity to express our sincere appreciation to all RIKEN researchers who participated in the survey.

2025-12-04

Seishiro Ono receives the Young Scientist Award of the Physical Society of Japan

Seishiro Ono (Assistant Professor, The University of Tokyo/Visiting Scientist, RIKEN iTHEMS) has received the Young Scientist Award (Division 4) presented by the Physical Society of Japan (JPS). The awarded research is titled “Classification of Topological Superconducting Phases by Symmetry Indicators.” This award recognizes outstanding young researchers under the age of 37 who are expected to contribute to the future of physics. Ono was recognized for his pioneering theoretical work on topological superconductors. Congratulations, Seishiro!

2025-11-13

The 1st Joint General Meeting of RIKEN Quantum and the QII RIKEN User Group on October 24, 2025

On Friday, October 24, the 1st Joint General Meeting of RIKEN Quantum and the QII RIKEN User Group was held at Okochi Hall on the RIKEN Wako campus, bringing together RIKEN researchers who utilize the ibm_kawasaki quantum computer. The meeting featured lively discussions on quantum computing research at RIKEN across a wide range of disciplines, including condensed matter physics, particle, nuclear and astrophysics, biomedical sciences, and the humanities. With over 60 participants, including members from IBM Quantum, the event was a great success. This meeting is expected to further accelerate the development of quantum computing research at RIKEN in the future.

2025-11-12

Physicists’ Dialogue: Discussing Quantum Gravity and Black Holes — PART Ⅱ (in Japanese)

Physicists’ Dialogue: Discussing Quantum Gravity and Black Holes — PART Ⅰ (in Japanese)

Interview with Mathematician Taketo Sano [PART Ⅱ] (in Japanese)

Physicists’ Dialogue: Discussing Quantum Gravity and Black Holes — Digest (in Japanese)

Introduction to “Black Hole Recorder” (in Japanese)

Interview with Mathematician Taketo Sano [PART I]

A Century of Quantum Mechanics

Interview with Mathematician Takashi Tsuboi [Part Ⅱ]

Interview with Physicist Yasunori Nomura - Part Ⅳ

Interview with Physicist Yasunori Nomura - Part Ⅲ

Interview with Mathematician Takashi Tsuboi [Part Ⅰ]

Interview with Mathematician Yuto Moriwaki [Part2]

Interview with Mathematician Yuto Moriwaki [Part 1]

Interview with Mathematician Eiji Inoue [Part 2] (in Japanese)

Interview with Physicist Yasunori Nomura - Part Ⅱ

The Connection Between Mathematics and Microbial Research: From Fisheries Science to the Path of Mathematics

Contributed to the 'One Poster per Household' Project – Like the Ones You See in Science Classrooms

Interview with Dr. Misako Tatsuma, a Planetary Formation Theorist

Interview with Mathematician Eiji Inoue [Part 1]

Interview with Physicist Yasunori Nomura - Part I

Interview with Physicist Ryo Namba [Part 2]

Interview with Physicist Ryo Namba [Part 1]

Interview with Ryosuke Iritani, Mathematical Biologist [Part 1]

Theoretical Physicist Tetsuo Hatsuda Interview Vol.2: About Research and Mathematics

Theoretical Physicist Tetsuo Hatsuda Interview Vol.1: About RIKEN iTHEMS

What about climate change in actuality?

Brunn-Minkowski inequality and the Borell-Brascamp-Lieb inequality

Aspects of Quantum Resonance Revisited

Distances and Durations: Cosmology 101

Symmetries of gravity

Birational classification of algebraic varieties

Gelfand duality

Scale transformations in physics and beyond

Machine Learning for Holographic Entanglement Inequalities

Describing Quantum Phenomena with Classical Gravity

Statistical Signatures of Quantum Chaos in Non-Hermitian Systems

Computers as a Playground for Mathematics

The Free Will Theorem in Quantum Mechanics

Renormalization revisited

Renormalization: Awareness of Ignorance

Recipe for soup of quarks and gluons

A subjective view on what is a quantum effect

Mathematical aspects of the entropic uncertainty relation

Forming black holes from stars

Singularity Theorems

Resurgence: making sense out of non-convergent series

How can we use a quantum computer to study the ground state of the hydrogen molecule?

Applications and Extensions of the Nielsen-Ninomiya Theorem in Condensed Matter Physics

COVID-19: then, now, and into the future

Exploring Quantum Spacetime

Classical simulations of quantum computers

When a Cretan says all Cretans are liars

Physical and local observables in gravitational theory

Can you hear the shape of a drum?

Quantum many-body physics with cold atoms

complexity in non-unitary dynamics of photons

Physics Through the Looking Glass

A new B.O.A.T. in astrophysics

Evolution and our daily rhythms

Area law of entanglement entropy in quantum many body systems and its implication in tensor network calculation

Comparison between conventional computers and quantum computers

A glimpse of enumerative geometry

Message-passing algorithms for graphical models

Canonical form of tensor networks in one and two dimensions

The basics of topological band theory

Building something from nothing: a mathematical framework for aperiodic/amorphous sets

Planetary lightning: Current State-of-the-art and outstanding questions

Collective Power of Science ~ from the High-Energy Atmospheric Physics to our New Exploration of the Universe ~

Morse theory and Floer theory

Knot theory and topological semimetals

On Dark Matter

Odd couples of interdisciplinary research

Khovanov homology theory - an introduction to categorification by Dr. Taketo Sano on May 13, 2022

Fundamentals Fest, mini Pre-event on Science "Exploring and Bridging: The Potential of Basic Science"

In Search of Pc pentaquark - Simulate Hadron Interactions with FUGAKU

AAS Journal Author Series: Hirotaka Ito on 2021ApJ…918...59I

Will Useless Knowledge Change the Future? - What is the Black Hole Recorder?

RIKEN 2019 (in Japanese)