Search Event

Targeting SARS-CoV-2 RNA: Insights for RNA-Directed Drug Discovery

July 31 (Thu) 13:00 - 14:30, 2025

Mariia Ivonina (Postdoctoral Fellow, Platform for Inter/Transdisciplinary Energy Research (Q-PIT), Kyushu University)

Traditional pharmacology fights virus infections by targeting proteins including enzymes, receptors, and structural proteins to break up the viral machinery. Nucleic acid-targeting therapies, on the other hand, can act directly on the genetic code of viruses, blocking their replication or translation in host cells. Coronaviruses and HIV are examples of RNA viruses that use a process called -1 programmed ribosomal frameshifting (-1 PRF) to produce their viral proteins. In this process, the translating ribosome is forced to shift into the alternative reading frame, replicating mRNA in the wrong order. Using small-molecule compounds to block this mechanism could be a promising way to neutralize such viruses. It is difficult to experimentally study the interactions between RNA and a drug candidate to understand where the drug binds and how it changes the shape of the viral RNA. I will discuss how Molecular Dynamics simulations are used to explore the conformational dynamics of mRNA structural elements and to investigate what happens when an antiviral agent binds to it. Additionally, I will show how the quantum-chemical orbital interaction analysis we developed, called Through-Space/Through-Bond Energy Decomposition Analysis (TS/TB-EDA), reveals which RNA nucleotides, at the atomic level, are critical for binding. This molecular modelling approach reveals strategies for targeting structured RNA elements — a crucial step toward expanding the arsenal of RNA-targeting therapeutics for future pandemics.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

iTHEMS NOW & NEXT 2025

July 24 (Thu) - 25 (Fri) 2025

We will hold this fiscal year’s annual in-house gathering, “iTHEMS NOW & NEXT,” as follows. This event is a rare opportunity for all iTHEMS members, including visiting researchers, to gain a comprehensive overview of iTHEMS’s current activities and future directions. Program July 24th 9:30-9:45 Opening by Director Iso 9:45-10:10 Keynote lecture Sonia Mahmoudi 10:10-10:35 Keynote lecture Masazumi Honda 10:35 20-min break 10:55 Fundamental Quantum Science Program (FQSP) introduction Working Group introduction 5-min each 11:30 Lunch break 13:30 Teams introduction part 1 RIKEN-Berkeley Center RIKENｰBerkeley Center (Shigehiro Nagataki) Mathematical Application Research Team (Motoko Kotani / Tsukasa Tada) 13:50 11 SG Presentation 5 min each 14:45 break 15:00 Flash talks & Poster session 18:00 Reception July 25th 9:30 Keynote lecture Yuto Yamamoto 9:55 Keynote lecture Kyosuke Adachi 10:20 break 10:40　Teams introduction part 2 Prediction Science Research Team (Takemasa Miyoshi) Medical Science Deep Learning Team (Jun Seita) Medical Science Data-driven Mathematics Team (Eiryo Kawakami) Quantum Mathematical Science Team (Tetsuo Hatsuda) Mathematical Social Science Team (Yohsuke Murase) 11:30 Lunch 13:30 Flash Talk & Poster presentation 16:30 Concluding remark

Venue: 2F Large Conference Room, Administrative Headquarters, RIKEN Wako Campus (Main Venue) / via Zoom

Event Official Language: English

Bridging applied math and quantum many-body physics and beyond via tensor methods

July 23 (Wed) 16:00 - 17:00, 2025

Hiroshi Shinaoka (Associate Professor, Department of Physics, Saitama University)

In modern physics, high-dimensional functions and operators naturally arise in a wide range of contexts, including turbulence simulations, parameter-dependent partial differential equations (PDEs), and quantum field theory. Efficient representations and computations with such high-dimensional objects pose major challenges across disciplines. Dimensionality reduction techniques such as the Quantics Tensor Train (QTT) [1] and Tensor Cross Interpolation (TCI) [2] were originally developed in applied mathematics. In our work, we have extended these methods to quantum many-body problems, demonstrating their effectiveness in handling complex high-dimensional structures in theoretical physics [3–10]. Given their generality, QTT and TCI are expected to find applications beyond quantum theory itself, in fields such as statistical field theory, model reduction, and control of complex systems, where similar high-dimensional structures emerge. This presentation will first review the computational bottlenecks that arise in quantum many-body simulations and other high-dimensional problems. Then, we will introduce QTT and TCI from a broader, method-oriented perspective, aiming to bridge applied mathematics and quantum theoretical physics.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Mesoscopic transport via one-dimensional chain with Localized two-body loss

July 23 (Wed) 10:00 - 11:30, 2025

Kensuke Kakimoto (Ph.D. Student, Faculty of Science and Engineering, School of Fundamental Science and Engineering, Waseda University)

Mesoscopic transport has long served as a powerful probe into the quantum behavior of matter; however, the role of dissipation in such systems remains unresolved. In recent years, quantum simulations of mesoscopic systems with ultracold atomic gases have made significant progress, particularly through the use of optical tweezers to induce local dissipation via atom loss. In this talk, we discuss a two-terminal mesoscopic system in which two-body loss occurs locally at the center of a one-dimensional chain, modeling a dissipative quantum point contact. To analyze this setup, we employ the Keldysh Green’s function formalism in combination with a noise-field representation of Lindblad dynamics. Our analysis reveals that the dissipation strength depends on the occupation number of the central dissipative site, leading to a weaker suppression of particle current in the weakly dissipative regime compared to the case of one-body loss.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

A free probability approach to quantum chaos in random matrix ensembles

July 22 (Tue) 16:00 - 17:00, 2025

Pratik Nandy (Postdoctoral Researcher, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

In free probability theory, quantum chaos is marked by “free independence” between observables at early and late times, causing certain statistical measures (cumulants) to vanish. Motivated by this, we study the statistics of a time-evolved operator in the Rosenzweig-Porter (RP) random matrix ensembles. Analyzing operator statistics for different spin operators across these regimes reveals close alignment with free probability predictions in the ergodic phase, contrasted by persistent deviations in the fractal and localized phases even at late times. Using the distance measures and statistical methods, we define and characterize the onset of the free time in the ergodic phase. The talk is based on arXiv: 2506.04520.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Detectability of post-Newtonian classical and quantum gravity via quantum clock interferometry

July 22 (Tue) 14:00 - 15:00, 2025

Eyuri Wakakuwa (Associate Professor, Department of Mathematical Informatics, Graduate School of Informatics, Nagoya University)

Understanding physical phenomena at the intersection of quantum mechanics and general relativity remains a major challenge in modern physics. While various experimental approaches have been proposed to probe quantum systems in curved spacetime, most focus on the Newtonian regime, leaving post-Newtonian effects such as frame dragging largely unexplored. In this study, we propose and theoretically analyze an experimental scheme to investigate how post-Newtonian gravity affects quantum systems. We consider two setups: (i) a quantum clock interferometry configuration designed to detect the gravitational field of a rotating mass, and (ii) a scheme exploring whether such effects could mediate entanglement between quantum systems. Due to the symmetry of the configuration, the proposed setup is insensitive to Newtonian gravitational contributions but remains sensitive to the frame-dragging effect. Assuming the validity of the quantum equivalence principle, this approach may provide insights not only into the quantum nature of gravity but also into whether spacetime itself exhibits quantum properties. However, our analysis reveals that, within realistic experimental parameters, the expected effects are too small to be detected. We discuss possible interpretations of this undetectability, and its implications for tests of quantum gravity.

Venue: #445--447, 4F, Main Research Building (Main Venue) / via Zoom

Event Official Language: English

What is “Quantum”!?: RIKEN Symposium Commemorating 100 Years of Quantum Science

July 12 (Sat) 13:00 - 17:00, 2025

Makoto Kobayashi (Director Emeritus, Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University)
Yasunori Nomura (Professor/Director, Berkeley Center for Theoretical Physics, University of California, Berkeley, USA)
Kenji Ito (Professor, Division of Contemporary Culture, Graduate School of Letters, Kyoto University)
Miho Hatanaka (Professor, Department of Chemistry, Faculty of Science and Technology, Keio University)
Norio Kawakami (Deputy Director, Fundamental Quantum Science Program, TRIP Headquarters, RIKEN)
Yasushi Okada (Deputy Director, RIKEN Center for Biosystems Dynamics Research (BDR))
Kouichi Hagino (Professor, Graduate School of Science, Kyoto University)
Shigeki Takeuchi (Professor, Graduate School of Engineering, Kyoto University)
Yasunobu Nakamura (Director, RIKEN Center for Quantum Computing (RQC))
Makoto Gonokami (President, RIKEN)

In celebration of the 100th anniversary of the birth of quantum science, the United Nations General Assembly has declared 2025 as the International Year of Quantum Science and Technology, coordinated by UNESCO. To mark this occasion, we will host a public symposium entitled: “What is “Quantum”!?: RIKEN Symposium Commemorating 100 Years of Quantum Science”, aimed at the general public. The talks will be conducted in Japanese. For more details and to register, please visit the official website via the related link.

Venue: via Zoom

Event Official Language: Japanese

RIKEN Theory Symposium

July 9 (Wed) - 10 (Thu) 2025

This symposium will bring together leading theorists from the fields of artificial intelligence, quantum information, quantum field theory, quantum gravity, and related areas of mathematics. It aims to stimulate interactions and collaborations across these diverse fields by fostering cross-disciplinary dialogue. It is organized by RIKEN's Pioneering Research Institute (PRI) together with the Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), and the Center for Advanced Intelligence Project (AIP). July, 9th (Wed.) 9:20- 9:30 Opening Remarks Dr. Hirosi Ooguri 9:30 - 10:15　Daniel Jafferis, “Tensor models for 3d gravity” 10:45 - 11:30 Sameer Murthy, “Supersymmetric index of black holes and black strings” Transportation by bus from Wako-campus is available for up to 60 people. Special AIP-PRI-iTHEMS joint seminar Venue: Tokyo Open Space (RIKEN Nihonbashi Campus) 14:30 - 15:15 Sergei Gukov, “Math + AI = AGI” 15:15 - 16:00 Masazumi Honda, “Fracton topological phases and Foliated field theories” 16:30 - 17:15 Richard Kueng, “Learning to predict ground state properties of gapped Hamiltonians” *Due to building access restrictions, this session is open only to participants of the morning session, RIKEN affiliates, or those who have completed the registration form. If you wish to attend, please register via the Related Links section below. July, 10th (Thur.) 9:30 - 10:15 Yifan Wang, “Pinning Defects, Fusion and Factorization” 10:45 - 11:30 Yichul Choi, “Non-Invertible Symmetry and Entanglement Entropy” 11:45 - 12:30 Yuya Kusuki, “Non-invertible Symmetries on Non-orientable Surfaces” 14:00 - 14:45 Heeyeon Kim, “3d TFTs from 4d N=2 BPS particles” 15:15 -16:00 Yuto Moriwaki, “On mathematical formulations of conformal field theory” 16:00 - 16:45 Kantaro Ohmori, “Higher Representation Theory and Excitations of Gauge Theories” 16:45 -16:55 Closing Remarks by Dr. Motoko Kotani Organizer: RIKEN Pioneering Research Institute (PRI) Co-organizers: RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) RIKEN Center for Advanced Intelligence Project (AIP)

Venue: Suzuki Umetaro Hall / Tokyo Open Space (COREDO Nihonbashi)

Event Official Language: English

On the Entanglement and Energy Dynamics of Continuous Floquet-driven CFTs

July 8 (Tue) 13:00 - 14:00, 2025

Yu-Xuan Zhang (Postdoctoral Fellow, Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, China)

A key approach to studying non-equilibrium quantum many-body systems is to suddenly alter their Hamiltonian and observe the resulting dynamical evolution. A single change is called a "quench", while periodic changes are termed "Floquet driving". Recently, Floquet driving protocols in two-dimensional conformal field theories (CFTs) have attracted widespread attention due to their exact solvability and rich phase structure. However, most studies are limited to discrete-type driving (e.g., as a square wave) and the associated stroboscopic dynamics (i.e., evolution at integer multiples of the driving period). A key obstacle is that a generic continuous driving is rarely analytically tractable. In this talk, I will introduce a class of exactly solvable continuous Floquet driving protocols. I will discuss the energy and entanglement dynamics under these protocols in 2D CFTs, as well as their holographic duals. Crucially, the results show that stroboscopic dynamics, if overinterpreted, can qualitatively misrepresent the system’s true continuous-time evolution.

Venue: via Zoom / #359, Seminar Room #359

Event Official Language: English

Computational Problems in Post-Quantum Cryptography

July 7 (Mon) 15:30 - 17:00, 2025

Tsuyoshi Takagi (Professor, Department of Mathematical Informatics, The University of Tokyo)

The security of current public-key cryptosystems relies on the hardness of factoring large integers or solving discrete logarithm problems. However, these computational problems can be solved in polynomial time using a quantum computer. This vulnerability has prompted research into post-quantum cryptography (PQC) using alternative mathematical problems that are secure in the era of quantum computers. In this talk, we give an overview of recent developments in the research on PQC. We explain a standardization project of PQC conducted by the National Institute of Standards and Technology (NIST). We then introduce an efficient digital signature, QR-UOV, based on the hardness of solving a system of multivariate quadratic polynomial equations over a finite field (the MQ problem). We also introduce a computational challenge problem, Fukuoka MQ Challenge, which aims at evaluating the hardness of the MQ problem with practical parameters.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Boundary Scattering and Non-invertible Symmetries in 1+1 Dimensions

July 4 (Fri) 14:00 - 15:00, 2025

Soichiro Shimamori (Ph.D. Student, Graduate School of Science, Osaka University)

Recent studies by Copetti, Córdova and Komatsu have revealed that when non-invertible symmetries are spontaneously broken, the conventional crossing relation of the S-matrix is modified by the effects of the corresponding topological quantum field theory (TQFT). We extend these considerations to (1+1)-dimensional quantum field theories (QFTs) with boundaries. In the presence of a boundary, one can define not only the bulk S-matrix but also the boundary S-matrix, which is subject to a consistency condition known as the boundary crossing relation. We show that when the boundary is weakly-symmetric under the non-invertible symmetry, the conventional boundary crossing relation also receives a modification due to the TQFT effects. As a concrete example of the boundary scattering, we analyze kink scattering in the gapped theory obtained from the Φ(1,3)-deformation of a minimal model. We explicitly construct the boundary S-matrix that satisfies the Ward-Takahashi identities associated with non-invertible symmetries. This talk is based on the collaboration with Satoshi Yamaguchi.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Quantum Computing Algorithms and Institute of Mathematics-for-Industry

July 3 (Thu) 15:30 - 17:00, 2025

Hiroyuki Ochiai (Professor, Institute of Mathematics for Industry, Kyushu University)

This is the kickoff talk of the Kyushu University Collaboration Team, which aims to foster communication between iTHEMS and IMI. I will introduce some of IMI's activities and organization, as well as my own work, including research on quantum algorithms that began with the launch of the Quantum Computing System Center in 2022.

Venue: #345-347, 3F, Main Research Building

Event Official Language: English

Exact WKB as unified analytic structure for resonance physics

June 27 (Fri) 15:00 - 17:00, 2025

Okuto Morikawa (Special Postdoctoral Researcher, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

We develop a unified framework for analyzing quantum mechanical resonances using the exact WKB method. The non-perturbative formulation based on the exact WKB method works for incorporating well-established phenomenological regularizations, the ABC theorem (proof of the completeness of Hilbert space), and the rigged Hilbert space in resonant phenomena. By examining the inverted Rosen-Morse potential, we illustrate how the exact WKB analysis captures resonant phenomena rigorously. Also, we clarify the corresponding linear spaces defined in each step of the exact WKB manipulations. The complementarity between the essential analyticity for resonance and the ABC theorem leads us to construct a modified Hilbert space called the rigged Hilbert space within the exact WKB framework. This offers a deeper understanding of resonant states and their analytic structures. Our results provide a concrete demonstration of the non-perturbative accuracy of exact WKB methods in unstable quantum systems.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

A diagrammatic approach to the Rasmussen invariant via tangles and cobordisms

June 26 (Thu) 15:00 - 17:00, 2025

Taketo Sano (Research Scientist, Mathematical Application Research Team, Division of Applied Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

Rasmussen’s s-invariant is an integer-valued knot invariant derived from Khovanov homology, and it has remarkable applications in topology, such as providing a combinatorial reproof of the Milnor conjecture. Although the s-invariant is defined using the quantum filtration of the homology group, it is difficult to interpret it geometrically. In this talk, we give a cobordism-based interpretation of the s-invariant based on Bar-Natan’s reformulation of Khovanov homology via tangles and cobordisms. This interpretation allows for the computation of the s-invariant from a tangle decomposition of the knot. As an application, we demonstrate that the s-invariants of 3-strand pretzel knots can be computed by hand.

Venue: #345-347, Main Research Building, RIKEN Wako Campus (Main Venue) / via Zoom

Event Official Language: English

Simulating the spread of infection in networks with quantum computers

June 26 (Thu) 13:00 - 14:00, 2025

Xiaoyang Wang (Postdoctoral Researcher, Quantum Mathematical Science Team, Division of Applied Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

Many classical stochastic processes can be modeled as Markovian processes, including the spreading of infection in networks. Simulating the Markovian processes using classical computers is generally unscalable for large networks. In this seminar, I will introduce the Hamiltonian evolution on quantum computers and how the Markovian spreading of infection can be efficiently simulated using the Hamiltonian evolution. In particular, we analytically and numerically analyze the evolution of a specifically designed Hamiltonian, and prove that the evolution simulates a classical Markovian process, which describes the well-known epidemiological stochastic susceptible and infectious (SI) model. As an example, we simulate the infection spreading process of the SARS-CoV-2 variant Omicron in a small-world network. The simulation results are qualitative consistent with the infection spreading in the west coast of USA.

Venue: via Zoom / Seminar Room #359

Event Official Language: English

Generative Models for Statistical Field Theories

June 25 (Wed) 15:00 - 16:00, 2025

Lingxiao Wang (Research Scientist, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

In the final talk of the DEEP-IN series, we will explore the role of generative models in learning phase transitions and sampling in lattice systems. First, we demonstrate how generative models can serve as global samplers by learning the underlying probability distributions. This enables the sampling of configurations more efficiently for lattice field theories. We will also demonstrate how the ferromagnetic phase transition, the Kosterlitz-Thouless transition, and quantum phase transitions can be identified from generative models. I will briefly introduce generative diffusion models, which can be interpreted as a stochastic quantization scheme. This opens a new path for understanding deep generative models. This is an informal seminar, we will start with the methodology and some practical examples, and finally reserve time for everyone interested to discuss it together.

Venue: #345-347, Main Research Building, RIKEN Wako Campus (Main Venue) / via Zoom

Event Official Language: English

Condensed-Matter Physics of Neutron Stars 2

June 25 (Wed) 14:00 - 16:30, 2025

Daisuke Inotani (Postdoctoral Researcher, Research and Education Center for Natural Sciences, Keio University)

Neutron stars, the most compact stars in the Universe, are composed of various matter. However, due to their extremely low temperatures and high densities, they exhibit strong interactions and condensed states. Knowledge of condensed-matter physics is essential for describing such quantum matter. In this lecture, theoretical aspects of condensed-matter physics relevant with neutron stars, through active discussion with participants.

Venue: #359, 3F, RIKEN Wako Campus (Main Venue) / via Zoom

Event Official Language: Japanese

Condensed-Matter Physics of Neutron Stars 1

June 25 (Wed) 10:00 - 12:30, 2025

Hiroyuki Tajima (Assistant Professor, Graduate School of Science, The University of Tokyo)

Neutron stars, the most compact stars in the Universe, are composed of various matter. However, due to their extremely low temperatures and high densities, they exhibit strong interactions and condensed states. Knowledge of condensed-matter physics is essential for describing such quantum matter. In this lecture, theoretical aspects of condensed-matter physics relevant with neutron stars, through active discussion with participants.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: Japanese

Spectral flow and applications

June 23 (Mon) 14:00 - 16:00, 2025

Christopher Bourne (Associate Professor, Institute of Liberal Arts and Sciences, Nagoya University)

Given a family of symmetric matrices indexed by a parameter (e.g. time, external field), changing this parameter will cause the eigenvalues to move along the real axis. The spectral flow tracks these eigenvalues and counts how many cross the point 0. This idea turns out to be very useful for both pure mathematics as well as applications to physics and elsewhere. In this talk, I will introduce the spectral flow and how it can be generalised to a variety of settings that are also relevant for applications in quantum physics.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building (Main Venue) / via Zoom

Event Official Language: English

Black hole states at finite N

June 18 (Wed) 16:30 - 17:30, 2025

Sunjin Choi (Postdoctoral Fellow, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo)

We study new cohomologies for the local BPS operators of the maximal super-Yang-Mills theory to better understand the black hole microstates. We first analyze the index of these black hole operators and explicitly construct their cohomologies to study how they imitate the quantum black holes. We find many towers of states and partial no-hair behaviors where certain gravtions are forbidden to dress these black hole operators. This qualitatively agrees with the behavior of the perturbative hairy BPS black holes or the so-called grey galaxies. Throughout this talk, we mainly focus on a subsector of the field theory corresponding to the BMN matrix theory, which exhibits a black hole-like entropy growth at large N.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English