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Causality Constraints on Black Hole Thermodynamics in Nonlinear Electrodynamics

2026年3月6日(金) 15:30 - 17:00

吉村 果保 (東京大学 大学院総合文化研究科 博士課程)

Black holes exhibit thermodynamic properties and provide an important window into the quantum aspects of gravity. In this context, nonlinear electrodynamics (NLED) offers a useful framework for constructing and analyzing charged black-hole solutions beyond Maxwell theory. Requiring causality - namely, excluding superluminal signal propagation - imposes nontrivial constraints on the allowed form of the NLED Lagrangian. In this talk, we focus on two quantities: the charge-to-mass ratio and the entropy density (entropy-to-mass squared ratio). The charge-to-mass ratio is expected to obey a monotonic behavior consistent with the Weak Gravity Conjecture, while the entropy density is also anticipated to be monotonic, reflecting the expectation that higher-energy effective theories contain more degrees of freedom. We show that these monotonic behaviors follow directly from the causality constraints on the NLED sector.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Non-perturbative geodesic length in JT gravity and universal time evolution of holographic complexity

2026年3月2日(月) 16:00 - 17:00

渋谷 翔之 (名古屋大学 博士課程)

The interplay between black hole interior dynamics and quantum chaos provides a crucial framework for probing quantum effects in quantum gravity. According to the holographic "Complexity=Volume" proposal, we investigated non-perturbative generating function of geodesic length in Jackiw-Teitelboim (JT) gravity to uncover universal signatures of quantum chaos and quantum complexity. We observed that the generating function interpolates between two major probes of quantum chaos - spectral form factor and complexity - highlighting its utility as a probe of chaotic spectrum in quantum gravity. Generalizing the result to general chaotic systems, we demonstrated that time evolution of the complexity is universally governed by a certain pole structure of observables, suggesting a validity of wide class of observables as a probe of quantum chaos in quantum gravity.

会場: via Zoom / セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

理化学研究所-奈良女子大学理学部合同 ダイバーシティ推進ワークショップ 2026

2026年3月2日(月) - 3日(火)

理化学研究所数理創造研究センター(iTHEMS)と奈良女子大学理学部は、理化学研究所ダイバーシティ推進室の後援を得て女性研究者育成事業を進めている。その一環として、奈良女子大学の学部生・大学院生21名が、理化学研究所和光キャンパスの複数の研究室を訪問し、研究内容について質疑を行うとともに、iTHEMSの研究者とワークショップを開催する。 主催：理化学研究所数理創造研究センター、奈良女子大学理学部 3月2日（月） 13:15-14:15 脳神経科学研究センター（CBS）（C56 池之端棟） 多階層精神疾患研究チーム（林朗子チームディレクター） 14:30-15:45 数理創造研究センター(iTHEMS) (C01 研究本館、4階435-437号室) iTHEMSの紹介：初田哲男（iTHEMS数理展開部門長） 講演と質疑 大矢めぐみ (iTHEMS医科学データ駆動数理チーム 特別研究員) 16:00-17:30 数理創造研究センター(iTHEMS) (C01 研究本館、4階435-437号室) 講演と質疑：レオ・シュパイデル（iTHEMS ECL研究ユニットリーダー） 　 18:00-20:30 情報交換会（C01, 研究本館3F東側（大河内ホール側）） 3月3日（火） 9:00-10:30 仁科センターRIBF施設 (RNC) 11:15-12:00 量子コンピュータセンター(RQC) 光量子制御研究チーム（米澤 英宏チームディレクター）

会場: 理化学研究所 和光キャンパス

イベント公式言語: 日本語

RIKEN iTHEMS-Kyoto University joint workshop on Asymptotics in Astrophysics and Cosmology

2026年3月2日(月) - 4日(水)

This joint workshop will bring together physicists and mathematicians who work with asymptotics and perturbation theory techniques. This includes theorists in cosmology, high energy physics, quantum gravity, solar physics, astrophysics. Workshop overview Over three days, there will be approximately 15 invited (1 hour slot) or contributed (20-30 min slot) talks about: Fundamental asymptotics and perturbation theory techniques used in theoretical physics. Various applications of asymptotics and perturbation theory techniques in (wave transport or oscillation related) astrophysics and cosmology eigenvalue problems. The workshop will also feature hands-on Mathematica and Python tutorials introducing: Practical use of WKB methods in applied mathematics for any “Schrodinger-like” wave equations, Resummation methods in high energy theory, Deriving normal modes in stars, and their application to tidal evolution in binary star or planet systems, Eigenvalue problems in core collapse supernova theory.

会場: 融合連携イノベーション推進棟（IIB） 8階

イベント公式言語: 英語

Testing the quantum nature of gravity with optomechanical systems

2026年2月26日(木) 10:00 - 12:00

道村 唯太 (東京大学 大学院理学系研究科 物理学専攻 助教)

Quantum gravity remains one of the major challenges in modern physics. Even at the most fundamental level, there is no experimental confirmation of whether a mass placed in a spatial superposition generates a corresponding superposition of gravitational fields. In recent years, experiments aiming to create gravity-induced quantum entanglement have attracted significant attention as a way to probe the quantum nature of non-relativistic gravity. In particular, optomechanical systems, which exploit the interaction between light and mechanical oscillators, provide a promising platform for such studies. We are pursuing experiments at the milligram scale, which lies between the smallest mass scale at which classical gravity has been tested and the largest mass scale at which quantum states of mechanical oscillators have been realized [1]. In this seminar, I will discuss experimental approaches to testing the quantum nature of gravity using suspended and levitated mirrors. I will also discuss our recent proposal to use inverted oscillators to enhance gravity-induced entanglement exponentially [2].

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Noninvertible symmetry protected topological phases on lattice

2026年2月25日(水) 10:30 - 11:30

Weiguang Cao (PD, Centre for Quantum Mathematics, University of Southern Denmark, Denmark)

The recent discovery of noninvertible symmetries—a radical extension of conventional symmetry—has challenged long-standing paradigms in condensed matter physics and quantum information and opened new territory in both theory and technology. Unlike ordinary symmetries, which can be inverted, these symmetries behave like projections (one-way operations) yet still strongly constrain quantum dynamics and enable new classes of phases and phase transitions. However, their role in organizing and stabilizing novel quantum phases remains poorly understood. One important example is a symmetry protected topological (SPT) phase, characterized by nontrivial edge modes and potential applications in quantum information. In this talk, I will discuss the classification of noninvertible symmetry-protected topological (NISPT) phases in both closed and open quantum systems using a duality-based method, and present concrete lattice realizations. These lattice models provide controlled playgrounds in which the physics of noninvertible symmetry can be explored numerically and, potentially, experimentally.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Spectral Codes : A Geometric Formalism for QEC

2026年2月19日(木) 15:00 - 16:30

菅野 聡 (ソフトバンク株式会社 先端技術研究所 研究員)

In this talk, I will introduce a novel geometric framework for quantum error correction based on spectral triples in noncommutative geometry. In this formulation, quantum error-correcting codes are described as spectral projections onto the low-energy eigenspaces of Dirac-type operators, where the separation between logical information and local errors is captured geometrically. This approach provides a unified spectral and geometric understanding of key properties such as code distance and error thresholds. Moreover, it accommodates various existing codes, including classical linear codes, stabilizer codes, GKP codes, and topological codes. This geometric perspective also suggests intriguing connections to deformation quantization and holographic quantum error correction, offering promising directions for future research.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Brainstorming session on data assimilation with quantum computing

2026年2月18日(水) 14:00 - 16:00

三好 建正 (理化学研究所 計算科学研究センター (R-CCS) データ同化研究チーム チームプリンシパル)

We will discuss the potential of quantum computing for applications in data assimilation.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Taming the Butterfly: A New "Duality Principle" Turns Chaos into Control

2026年2月18日(水) 13:00 - 14:00

三好 建正 (理化学研究所 計算科学研究センター (R-CCS) データ同化研究チーム チームプリンシパル)

Data Assimilation (DA) is the backbone of modern weather forecasting. It integrates observational data into computer simulations to synchronize the model with nature. The Duality Principle posits that chaos control is mathematically the "twin" (dual) of DA. Data Assimilation: Uses observations to synchronize the Model to Nature. Chaos Control: Uses interventions to synchronize Nature to a desired Model ("target trajectory"). "The butterfly effect has long been a symbol of unpredictability," says Dr. Miyoshi. "But I asked a simple question: If a butterfly's wings can change the future, does that not imply that with the right, tiny push, we could choose a better future?" Instead of suppressing the chaotic system with massive force, this method acts like mathematical judo—leveraging the system's inherent instability. By applying minute, calculated "interventions" (analogous to the butterfly's flap), the system can be guided toward a "target trajectory"—for instance, shifting real-world conditions just enough to align with a model-simulated scenario where a typhoon causes no damage. Once synchronized, control becomes much easier to maintain. This study establishes the theoretical foundation for "Control Simulation Experiments" (CSE), a framework previously proposed by Miyoshi’s team. It provides a roadmap for future disaster prevention research, moving beyond passive prediction to active mitigation. Beyond meteorology, this general framework is expected to serve as a universal tool for studying interventions in various chaotic systems, from ecosystems to economics. Following the seminar, we will hold an informal discussion (brainstorming) on data assimilation with quantum computing in the same room from 2-4 pm.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Recent progress in the resource theory of asymmetry and its applications

2026年2月12日(木) 13:30 - 15:00

田島 裕康 (九州大学 大学院システム情報科学研究院 情報学部門 准教授)

If you are not affiliated with RIKEN, please register using the registration form. Registration deadline: 12nd Feb. (Thu), 2026 Symmetry and symmetry breaking are among the central themes in physics and have attracted the interest of many physicists. Recently, the resource theory of asymmetry (RTA) [1-4], which approaches these issues from the perspective of resource theories, has been actively studied. In the past few years, several foundational advances have been made in this framework. In particular, the iid-complete monotone that plays a role analogous to entanglement entropy has been identified for arbitrary compact Lie groups [2] as well as for arbitrary finite groups [3]. The resolution for compact Lie groups includes, as a corollary, a solution to the Marvian–Spekkens conjecture [4]. Building on this theoretical foundation, several developments related to the Wigner–Araki–Yanase (WAY) theorem [5-7] have also been obtained. These include extensions of the WAY theorem to the implementation of arbitrary unitary gates [8], and a unification of the WAY-type theorems, i.e. the WAY theorem, the Eastin–Knill theorem (a fundamental limitation on error correction under symmetry) [9], and the above unitary-gate results. The unification is formulated a universal trade-off inequality relating symmetry, irreversibility, and quantumness for arbitrary quantum dynamics [10]. Using this tradeoff relation, the WAY-type limitations can now be applied, for example, to quantum thermodynamics[11] and black hole evaporation [10] etc. If time permits, I will also briefly touch upon some other recent developments, such as extensions of the above tradeoff and the WAY theorem to general resource theory beyond symmetry [12].

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Quantum Electrodynamics of Strong Laser-Matter Interaction: The Ongoing Journey and Beyond

2026年2月10日(火) 10:00 - 12:00

Ciappina Marcelo (Professor, Guangdong Technion, China)

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Scalable Simulation of Quantum Many-Body Dynamics with Or-Represented Quantum Algebra

2026年2月4日(水) 14:30 - 16:00

Lukas Broers (理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)

High-performance numerical methods are essential for advancing quantum many-body physics, as well as for enabling the integration of supercomputers with emerging quantum computing platforms. We have developed a scalable and general-purpose numerical framework for quantum simulations based on or-represented quantum algebra (ORQA). This framework applies to arbitrary spin-systems and naturally integrates with quantum circuit simulation in the Heisenberg picture, particularly relevant to recent large-scale experiments on superconducting qubit processors [Kim et al., Nature 618, 500 (2023)]. As a benchmark, we simulate the kicked Ising model on a 127-qubit heavy-hexagon lattice, successfully tracking the time-evolution of local magnetization using up to one trillion Pauli strings. Our simulations exhibit strong scaling up to 2^17 parallel processes with near-linear communication overhead. Further, we show that our framework is naturally extended to a broader range of quantum systems, superseding the capabilities of recently established Pauli propagation methods. We present possible future directions on how to utilize our algorithm.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

From Wavefunction Sparsity to Quantum Filter-Assisted Subspace Diagonalization

2026年2月4日(水) 13:00 - 14:30

Han Xu (理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)

Subspace diagonalization techniques based on quantum sampling, such as quantum selected configuration interaction (QSCI) and sample-based quantum diagonalization (SQD), are a class of quantum-centric algorithms for approximating ground-state energies of many-body systems. One of the foundational bottlenecks for SQD is due to the lack of compactness of the ground-state wavefunctions. In this talk, we will introduce a filter-assisted SQD protocol that enhances the wavefunction sparsity through a quantum-circuit transformation of the Hamiltonian. Using the Gini coefficient as a robust sparsity measure, we clarify how sparsity determines the resource requirements of SQD. To construct the quantum filter, we develop a tensor-network-based automatic circuit-encoding algorithm that encodes the target matrix product states with controllable fidelity. We benchmark the method on the quantum Ising model under the transverse and longitudinal fields, using both numerical simulations and experiments on IBM quantum hardware. Our results show that the filter-assisted protocol reduces energy-estimation errors by orders of magnitude and substantially lowers the overhead of measurement compared with standard SQD, which highlight the potential of filter-assisted protocol in quantum-centric computing for strongly correlated materials.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

International Workshop on Quantum Geometry

2026年2月3日(火) - 6日(金)

In recent years, quantum geometry has attracted a renewed interest as an important concept in physics, and is being actively studied in a wide variety of fields ranging from condensed matter physics to high-energy physics. This international workshop aims to invite researchers actively working at the forefront of quantum geometry research and hold intensive discussions, thereby providing an opportunity to facilitate mutual interaction that will lead to future collaborations. The workshop will cover a wide range of topics related to quantum geometry, as in condensed matter physics, AMO physics, quantum gravity, quantum information, etc.

会場: 情報基盤棟1階112 (C43) (メイン会場) / Satellite : 4F, "Common Space" of FQSP, Information Science Bldg.(C43)

イベント公式言語: 英語

Gauge fixing for open systems: A pathway to open gravity EFTs

2026年1月30日(金) 14:00 - 16:00

Maria Mylova (カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)

Understanding how to gauge-fix open quantum field theories is essential for building consistent open frameworks for cosmology and gravity, where gauge symmetry must coexist with dissipation and noise and decoherence. I will present our recent work developing explicit top-down constructions of open effective field theories (EFTs) for gauge degrees of freedom, with particular emphasis on the role of gauge fixing. We implement BRST quantisation on the Schwinger-Keldysh contour and show that the in-in boundary conditions reduce the doubled global BRST symmetry to a single diagonal copy. This diagonal BRST symmetry is nevertheless sufficient to guarantee that the influence functional remains gauge invariant under two independent gauge transformations, retarded and advanced, independently of the choice of initial state, the presence of symmetry-breaking phases, and whether the gauge theory is Abelian or non-Abelian. We further clarify how this is compatible with the decoupling limit, in which the global advanced symmetry is generically broken by the state. I will conclude by outlining bottom-up implications, and how these principles provide a systematic route to causal, gauge-invariant open EFTs suitable for cosmological and gravitational applications.

会場: 研究本館 4階 445-447号室 (Hybrid)

イベント公式言語: 英語

iTHEMS Cosmology Forum n°5 - Effective Field Theory approaches across the Universe

2026年1月29日(木) 10:00 - 17:00

青木 勝輝 (京都大学 基礎物理学研究所 基研特任助教)
野海 俊文 (東京大学 大学院総合文化研究科 准教授)
Lucas Pinol (CNRS Researcher, Laboratoire de Physique de l’École Normale Supérieure (LPENS), CNRS/École Normale Supérieure, France)

This fifth workshop will bring together researchers exploring the effective field theory (EFT) framework in diverse cosmological contexts (https://indico2.riken.jp/event/5435/overview). Topics will include EFT formulations of interacting dark matter and dark energy, open EFTs for gravity, and multi-field inflationary dynamics. By highlighting recent progress and open questions, the workshop seeks to bridge insights from the early and late universe through the unifying language of EFT. In addition to the invited talks, the workshop will feature a panel discussion designed to promote interaction between the speakers and participants. One of the key goals of this event is to foster collaboration among researchers working in neighboring fields, and to encourage participation from young and early-career researchers who are interested in, but may not yet have worked on, these themes. The workshop welcomes a broad audience with an interest in theoretical cosmology, gravitation, and quantum field theory. The workshops are organised by the Cosmology Study Group at RIKEN iTHEMS.

会場: 大河内記念ホール

イベント公式言語: 英語

DEEP-IN-iPI Joint Meeting

2026年1月26日(月) - 30日(金)

郭 星雨 (Lecturer, Institute of Quantum Matter, South China Normal University, China)
Gert Aarts (Professor, Department of Physics, Swansea University, UK)
施 舒哲 (Assistant Professor, Physics Department, Tsinghua University, Beijing, China)
Sung Hak Lim (Senior Researcher, Center for Theoretical Physics of the Universe (CTPU-PTC), Institute for Basic Science (IBS), Republic of Korea)
ジンヤン・リー (総合研究大学院大学 素粒子原子核コース 博士課程)
許 インイン (Research fellow, Department of Mathematics and Statistics, University of Helsinki, Finland)

The series of DEEP-IN meetings (Jan 26–30, 2026) are joint with UTokyo Institute for Physics of Intelligence (iπ), which is a multi-day scientific program bringing together researchers to explore quantum simulations, machine learning physics, and applications in particle and nuclear physics. The tentative schedule is, UTokyo-iπ Session (Venue: #512, Faculty of Science Bldg.1, School of Science, UTokyo) Day 1: Jan 26 (Mon) 14:30–16:00 Onset of Bjorken flow in a quantum many-body simulation of the massive Schwinger model, Shuzhe Shi Day 2: Jan 27 (Tue) 14:30–16:00 Physics of Diffusion Models, Gert Aarts 16:00–17:30 Discovering Symmetry from Energy-Based Diffusion Models, Jinyang Li RIKEN-iTHEMS Session (Venue: Seminar Room #359, Main Research Building) Day 3: Jan 28 (Wed) 14:30–16:00 Understanding Galactic Dark Matter with Generative Models, Sung Hak Lim 16:00–18:00 Free Discussion ML Physics-1 Day 4: Jan 29 (Thu) 10:00–11:30 Quantum Simulations of HEP and Beyond, Xingyu Guo 14:30–16:00 Physics of Machine Learning, Gert Aarts 16:00–17:30 Storage capacity of perceptron with variable selection, Yingying Xu Day 5: Jan 30 (Fri) 11:00–14:00: Free Discussion ML Physics-2

会場: via Zoom / セミナー室 (359号室) / 東京大学 本郷キャンパス 理学部１号館

イベント公式言語: 英語

New computational methods in quantum field theory 2026

2026年1月26日(月) - 28日(水)

Recent developments in quantum computers and related theoretical/technical advancements have brought attention to "new computational methods in quantum field theory" in the fields of high energy/nuclear physics. Main targets of this school are graduate students and postdocs. This school provides opportunities to discuss recent research trends and their applications through lectures by experts and presentations by participants. Lecturers: Junichi Haruna (University of Osaka) "Introduction to Quantum Error Correction (tentative)" Yoshimasa Hidaka (Yukawa Institute for Theoretical Physics/RIKEN iTHEMS) “Introduction to Hamiltonian Lattice Gauge Theory (tentative)” Tokiro Numasawa (University of Tokyo) "Open Majorana system (tentative)"

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Analog variational quantum eigensolver for neutral atomic quantum simulators

2026年1月20日(火) 10:00 - 12:00

長尾 一馬 (理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

A one-world interpretation of quantum mechanics

2026年1月16日(金) 14:00 - 16:00

Isaac Layton (東京大学 大学院理学系研究科 物理学専攻 ポスドク研究員)

The measurement problem arises in trying to explain how the objective classical world emerges from a quantum one. In this talk I’ll advocate for an alternative approach, in which the existence of a classical system is assumed a priori. By asking that the standard rules of probability theory apply to it when it interacts with a system linearly evolving in Hilbert space, I’ll show that with a few additional assumptions one can recover the unitary dynamics, collapse and Born rule postulates from quantum theory. This gives an interpretation of quantum mechanics in which classically definite outcomes are always assigned probabilities, rather than superpositions, giving one-world instead of many. The main technical tool used is a change of measure on the space of classical paths, the functional form of which characterises the quantum dynamics and Born rules of a class of quantum-like theories. Time allowing, I will also discuss how these results clarify which additional assumptions must be accepted if one wishes to seriously consider classical alternatives to quantum gravity.

会場: 研究本館 4階 445-447号室 / via Zoom

イベント公式言語: 英語