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Quantum Information: Entanglement of Mathematics & Physics

2026年9月21日(月) - 23日(水)

This workshop brings together mathematicians and physicists to explore the deep connections among quantum information, mathematics, and physics. Topics span quantum gravity, condensed matter physics, quantum computing, and quantum error correction, with an emphasis on the mathematical structures that underlie entanglement and quantum information across these fields. The program is designed to foster genuine cross-disciplinary dialogue, allowing ample time for discussion alongside formal talks. [Invited speakers] Akira Furusaki (RIKEN CEMS/iTHEMS) Marcel Franz (UBC / SBQMI) Ching-Kai Chiu (iTHEMS) Jasmin Bedow (UBC) Max McGinley (UBC) Yosuke Kubota (Kyoto University) Shunji Matsuura (RIKEN iTHEMS) Bartosz Regula (RIKEN RQC) Ryuji Takagi (University of Tokyo) Sisi Zhou (Perimeter Institute) Olivia Di Matteo (UBC / SBQMI) Daochen Wang (UBC Computer Science) Polina Feldmann (UBC) Masazumi Honda (RIKEN iTHEMS) Yasuyuki Kawahigashi (RIKEN iTHEMS) Carolyn Zhang (UBC) Masahito Yamazaki (Kavli IPMU, University of Tokyo) Aswin Parayil Mana (University of Tokyo) Alex May (Perimeter Institute) Masamichi Miyaji (RIKEN iTHEMS) Mark Van Raamsdonk (UBC Physics & Astronomy)

会場: University of British Colombia / via Zoom

イベント公式言語: 英語

Magic state distillation and cultivation #2

2026年9月10日(木) 13:30 - 17:00

平野 裕 (Research Scientist, Nanofiber Quantum Technologies)

本セミナーでは、誤り訂正において重要な概念である"distillation"や"cultivation"について講義形式で説明していただきます。対面およびZoomのハイブリット形式ですが、機器の都合によりZoom配信が困難な可能性がありますので、対面参加を推奨しています。 講義にあたって、以下の事項の理解は前提とします。 A. 量子計算の基礎 (quantum state, quantum gate, measurement, quantum circuit, Pauli gate, Clifford gate, Non-Clifford gate) B. 量子エラー訂正の概念（quantum error correction, decoding） これらは、Nielsen and Chuang [1] が最もまとまっています。 以下の事項は講義で紹介しますが、理解しているとより良いかもしれません。 C. 論理ゲート及び FTQC [1] D. surface code [2], [3] E. lattice surgery [4] なお、B-E については、https://docs.qc500.org/ の "Quantum Error Correction" にもまとまっています。 [1]: M. A. Nielsen and I. L. Chuang, Quantum Computation and Quantum Information (Cambridge University Press, 2000). [2]: A. Yu. Kitaev, “Fault-tolerant quantum computation by anyons,” Ann. Phys. 303, 2–30 (2003). [3]: H. Bombin and M. A. Martin-Delgado, "Optimal Resources for Topological 2D Stabilizer Codes: Comparative Study," Phys. Rev. A 76, 012305 (2007). [4]: D. Horsman, A. G. Fowler, S. Devitt, and R. Van Meter, "Surface code quantum computing by lattice surgery," New J. Phys. 14, 123011 (2012).

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: 日本語

Magic state distillation and cultivation #1

2026年9月10日(木) 10:30 - 12:00

平野 裕 (Research Scientist, Nanofiber Quantum Technologies)

本セミナーでは、誤り訂正において重要な概念である"distillation"や"cultivation"について講義形式で説明していただきます。対面およびZoomのハイブリット形式ですが、機器の都合によりZoom配信が困難な可能性がありますので、対面参加を推奨しています。 講義にあたって、以下の事項の理解は前提とします。 A. 量子計算の基礎 (quantum state, quantum gate, measurement, quantum circuit, Pauli gate, Clifford gate, Non-Clifford gate) B. 量子エラー訂正の概念（quantum error correction, decoding） これらは、Nielsen and Chuang [1] が最もまとまっています。 以下の事項は講義で紹介しますが、理解しているとより良いかもしれません。 C. 論理ゲート及び FTQC [1] D. surface code [2], [3] E. lattice surgery [4] なお、B-E については、https://docs.qc500.org/ の "Quantum Error Correction" にもまとまっています。 [1]: M. A. Nielsen and I. L. Chuang, Quantum Computation and Quantum Information (Cambridge University Press, 2000). [2]: A. Yu. Kitaev, “Fault-tolerant quantum computation by anyons,” Ann. Phys. 303, 2–30 (2003). [3]: H. Bombin and M. A. Martin-Delgado, "Optimal Resources for Topological 2D Stabilizer Codes: Comparative Study," Phys. Rev. A 76, 012305 (2007). [4]: D. Horsman, A. G. Fowler, S. Devitt, and R. Van Meter, "Surface code quantum computing by lattice surgery," New J. Phys. 14, 123011 (2012).

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: 日本語

The 11th Intensive Lectures on Quantum Gravity

2026年9月7日(月) - 9日(水)

初田 泰之 (立教大学 理学部 物理学科 准教授)

In the 11th event of the Intensive Lecture Series, organized by the Quantum Gravity Gatherings (QGG) study group at RIKEN iTHEMS, we will have Prof. Yasuyuki Hatsuda from Rikkyo University, who will deliver a three-day lecture series on the analytic methods in black hole perturbation theory. Black hole perturbation theory plays a very important role in the developments of modern physics. For instance, in gravitational wave astronomy, it can describe the ringdown phase during the merger events of binary black holes. As the frequency and decay rate of each quasinormal mode are unique to the remnant black hole, one can test extreme-gravity physics by extracting those modes from the ringdown signal. In addition, the computation of black hole quasinormal modes based on black hole perturbation theory has relations connecting to conformal field theories and even to the computations of tidal Love numbers. With the broad applications, we expect this lecture series to provide fresh perspectives to researchers across a wide range of fields and to inspire new directions in their own research. The lectures will be delivered in a blackboard-style format (in English), designed to foster interaction, active participation, and in-depth Q&A discussions. In addition, short talk sessions will be held, giving participants the opportunity to present briefly on topics of their choice. Through this informal and dynamic setting, we hope to spark active interactions among participants and create an environment where ideas can be shared openly and enthusiastically. This event will take place in person only. Target audience: Senior scholars, early-career researchers, and students are all warmly welcome. Registration deadline: July 31, 2026

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Cancellation of loop corrections to soft power spectrum of inflation

2026年9月3日(木) 16:30 - 18:00

洪 木子 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 特別研究員)

Inflation theory provides an explanation for the seeds of structure formation and inhomogeneities in the cosmic microwave background (CMB) through quantum fluctuations stretched to cosmological scales during inflation. Mechanisms that enhance small-scale curvature perturbations during inflation can lead to the formation of primordial black holes after horizon re-entry. Recently, some arguments have claimed that loop corrections from such enhanced small-scale fluctuations can give a scale-invariant contribution to the large-scale power spectrum and thereby spoil the inflationary prediction for the CMB. This appears to challenge the standard tree-level expectation that large-scale curvature perturbations are conserved on superhorizon scales in single-clock inflation, and has ignited discussion. In this talk, I will show that the scale-invariant contribution from the enhanced small-scale fluctuations indeed cancels, both in an explicit one-loop calculation and as a consequence of the diffeomorphism symmetry of General Relativity. This seminar is jointly organized by the iTHEMS–ABBL Joint Astro Study Group and the Cosmology Study Group.

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

Finite cut-off holography and Matrix models

2026年9月3日(木) 10:30 - 11:45

Sounak Pal (Student, Indian Institute of Technology Gandhinagar, India)

In this talk, I will discuss finite-cutoff models of two-dimensional topological gravity and their relation to random matrix theories. Random matrix models have emerged as a useful tool for understanding and refining semiclassical holographic dualities, particularly in low-dimensional quantum gravity. I will begin with a brief introduction to large-(N) matrix models and then describe their connection to low-dimensional topological quantum field theories. Along the way, I will highlight how introducing a finite cutoff can lead to significant modifications in the growth of the black-hole interior compared with the matrix-model description of pure JT gravity. Finally, I will discuss the relation between (TT-bar)-deformed Schwarzian theories and their gravitational bulk duals, emphasizing how these deformations provide an avenue for exploring finite-cutoff holography and possible departures from the standard JT-gravity picture.

会場: 研究本館 3階 359号室 / via Zoom

イベント公式言語: 英語

iTHEMS-UTokyo Intensive Lectures on Quantum Gravity

2026年8月31日(月) - 9月2日(水)

川合 光 (大阪公立大学 南部陽一郎物理学研究所 客員教授)

iTHEMS-UTokyo Intensive Lectures on Quantum Gravity (10th Quantum Gravity Gatherings Lecture Series) The 10th QGG Lecture Series is a special three-day installment of the intensive lecture series organized by the Quantum Gravity Gatherings (QGG) study group at RIKEN iTHEMS. This celebratory edition will feature Professor Hikaru Kawai from Nambu Yoichiro Institute of Theoretical and Experimental Physics (NITEP), who will deliver a series of lectures on themes related to quantum gravity. This lecture series will follow a style similar to Prof. Kawai's first QGG lectures, held three years ago at RIKEN (Wako) as the inaugural QGG event, which explored fundamental questions in quantum gravity, string theory, and the quantum universe. A distinctive feature of this 10th installment is that it will take place on the Komaba campus of The University of Tokyo, where one of the iTHEMS satellite offices is located. This will be the first QGG lecture series held outside Wako, with the aim of making the event more accessible to a broader group of participants. Format: Lectures will be given mainly in blackboard style and in English, encouraging active participation and in-depth Q&A discussions. Poster sessions will also be held, giving participants an opportunity to present their own work or topics of interest. These sessions are intended to foster communication and stimulate the exchange of ideas among participants. This event will take place in person only. Target audience: Senior scholars, early-career researchers, and students are all warmly welcome. Registration deadline: July 31, 2026

会場: 21 Komaba Center for Educational Excellence (21 KOMCEE) East Building, Room K214, Komaba Campus, The University of Tokyo

イベント公式言語: 英語

Scattering amplitude from quantum computing with reduction formula

2026年8月27日(木) 15:00 - 16:00

Wai Kin Lai (Lecturer, The University of Hong Kong, China)

In this talk, I will present a new general framework for computing scattering amplitudes in quantum field theory with quantum computers in a fully nonperturbative way. After giving a motivation for the application of quantum computing to particle physics, I will briefly introduce the basics of quantum computing. After that, I will give the details of the proposed quantum algorithm for calculating scattering amplitudes, which utilizes the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula. In this framework, one only has to construct one-particle states of zero momentum, and no wave packets of incoming particles are needed. The framework is able to incorporate scatterings of bound states, and is ideal for scatterings involving a small number of particles. This framework is expected to have particular advantages when applied to exclusive hadron scatterings. As a proof of concept, by simulations on classical hardware, I demonstrate that in the one-flavor Gross-Neveu model, the fermion propagator, the connected fermion four-point function, and the propagator of a fermion-antifermion bound state obtained from our proposed quantum algorithm have the desired pole structure crucial to the implementation of the LSZ reduction formula. Brief CV: Wai Kin Lai received PhD in physics at the University of Pittsburgh in 2016. He was a postdoctoral reseacher at the Technical University of Munich from 2016 to 2020. From 2020 to 2023, he was a postdoctoral researcher at South China Normal University, and was a visiting assistant researcher at the University of California, Los Angeles from 2022 to 2023. Wai Kin Lai is currently a lecturer at HKU SPACE in Hong Kong. Wai Kin Lai's research interests are applications of effective field theories of QCD to particle phenomenology and studies of nonperturbative physics with quantum computation.

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

UK-Japan Workshop on Quantum Gravity 2026

2026年8月24日(月) - 28日(金)

The universe at extremely early times is expected to be described by some theory of quantum gravity, although we still do not know precisely what quantum gravity actually is. In modern approaches to quantum gravity, the path integral point of view provides a fundamental framework towards answering this pressing question. However, an evaluation or even just a precise definition of the path-integral for a full-fledged quantum gravity is one of the most important open problems in modern theoretical physics. With the "UK-Japan Workshop on Quantum Gravity 2026" we want to bring together experts working on different aspects of the gravitational path-integral, such as Gravitational Scattering Amplitudes; Complex Geometries and Exact WKB; Quantum Cosmology; Exact Methods and Resurgence Analysis; with the long-term goal of providing innovative ways of tackling modern problems in quantum gravity. This workshop is the second event sponsored by the Royal Society International Collaboration Award Grant "Re-PaInt: A Resurgence Path-Integral approach to quantum gravity" shared between Masazumi Honda at Riken iTHEMS and Daniele Dorigoni at Durham University, and aimed at fostering and developing an international partnership between the two institutes, as well as the greater Japan and UK theoretical physics communities working on quantum gravity, broadly intended. The page for the 2025 meeting held at the RIKEN campus in Kobe can be found in the Related Links section below.

会場: Durham University

イベント公式言語: 英語

RIKEN–IPMU mini-workshop on QCA and K-theory

2026年8月24日(月) - 26日(水)

Three-day lecture series by Bowen Yang, based on joint work with Mattie Ji (arXiv:2602.16572 and arXiv:2606.19657), in which quantum cellular automata are classified by an algebraic K-theory spectrum.

会場: via Zoom / レクチャーホール、Kavli IPMU, 東京大学

イベント公式言語: 英語

The 3rd NCTS-iTHEMS Joint Workshop on Theoretical, Mathematical, and Computational Sciences

2026年8月18日(火) - 21日(金)

The 3rd NCTS-iTHEMS Joint Workshop will be held from August 18 to 21, 2026, at National Taiwan University. Following the previous two editions, which focused mainly on theoretical physics, this year’s workshop marks a new stage in the partnership between RIKEN iTHEMS and NCTS. In particular, the workshop follows the signing of the iTHEMS-NCTS Collaboration Research Agreement in April 2026, which aims to further strengthen researcher exchange, international workshops, and joint research activities. With the participation of both the NCTS Physics and Mathematics Divisions, this year’s workshop broadens its scope from theoretical physics to the wider interface among theoretical, mathematical, and computational sciences. Key topics include high-energy physics and gravity, condensed matter physics, quantum computing and information, geometry and topology, applied mathematics, machine learning, and scientific AI. The program will feature plenary lectures, research talks, and a poster session, providing a platform for interdisciplinary exchange and future collaborations between iTHEMS and NCTS. Registration is open to the public. Feel free to sign up if you're interested! Venue NCTS Physics Lecture Hall, 4th Floor, Cosmology Hall, NTU Speakers Plenary Speakers Tan Bui-Thanh (UT Austin) Etera Livine (ENS Lyon) Tzu-Chieh Wei (SUNY Stony Brook) Invited Speakers Chi-Kang Chang (RIKEN iTHEMS) Chien-Yu Chou (RIKEN iTHEMS) Antoine Diez (RIKEN iTHEMS) Keita Goto (RIKEN iTHEMS) Ryusuke Hamazaki (RIKEN iTHEMS) Masazumi Honda (RIKEN iTHEMS / Saitama U) Muzi Hong (RIKEN iTHEMS) Masaaki Imaizumi (RIKEN AIP / U of Tokyo) Derek Inman (RIKEN iTHEMS) Isao Ishikawa (Kyoto U) Riccardo Muolo (RIKEN iTHEMS) Álvaro Pastor-Gutiérrez (RIKEN iTHEMS) Wei-Hsiang Shao (RIKEN iTHEMS) Chuan-Tsung Chan (Tunghai University) Po-Yao Chang (NTHU) Heng-Yu Chen (NTU) Hao-Chung Cheng (NTU) Hao-Wei Huang (NTHU) Yi-Ping Huang (NTHU) Jer-Lai Kuo (AS) Chia-Hsiang Lin (NCKU) Chin-Hung Lin (NYCU) Yu-Chen Shu (NCKU) Cheng-Fang Su (NYCU) Chiao-Hsuan Wang (NTU) (In alphabetical order of surnames) Organizing Committee Chi-Kang Chang (RIKEN iTHEMS) Che-Yu Chen (RIKEN iTHEMS) Ching-Kai Chiu (RIKEN iTHEMS) (co-chair) Pei-Ming Ho (NTU/NCTS) Masazumi Honda (RIKEN iTHEMS) Chang-Tse Hsieh (NTU/NCTS) (co-chair) Ming-Lun Hsieh (NTU/NCTS) Isao Ishikawa (Kyoto U) Satoshi Iso (RIKEN iTHEMS) Min-Hsiung Lin (NCKU/NCTS) Yuki Yokokura (RIKEN iTHEMS) (In alphabetical order of surnames)

会場: NCTS Physics Lecture Hall, 4th Floor, Cosmology Hall, NTU

イベント公式言語: 英語

Four Fermi Theory in Four Dimensions is Renormalisable

2026年8月3日(月) 15:00 - 16:30

Charlie Cresswell-Hogg (Post-Doctoral fellow, Department of Physics, Sussex University, UK / Post-Doctoral fellow, Dortmund University, Germany)

We demonstrate the renormalisability of quantum field theories in four dimensions with elementary self-interacting Dirac fermions and to leading order in the limit of many fermion flavours Nf. Starting from the underlying divergence structure and using Gross-Neveu-type interactions as a template, we explain why extended four-fermion theories including higher-derivative interactions are well-defined, renormalisable, and predictive with only a few free parameters. We also provide the exact large-Nf leading beta functions of couplings and discuss quantum scaling dimensions, universality, 1/Nf corrections, and extensions to other types of four fermion interactions. Implications for effective theory and model building are indicated.

会場: via Zoom

イベント公式言語: 英語

Quantum Gravity and Emergent Cosmology: A Group Field Theory Perspective

2026年7月31日(金) 14:00 - 16:00

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

This seminar is the second part of a two-part mini-seminar series organized by the Quantum Gravity Gatherings study group. It is intended to have a more lecture-style format, with an extended duration of up to two hours. This will allow the speaker sufficient time to introduce the framework in a clear and pedagogical manner, while also leaving ample room for questions and discussion with the audience. Title: Quantum Gravity and Emergent Cosmology: A Group Field Theory Perspective Abstract: I will introduce the Group Field Theory (GFT) approach to quantum gravity, emphasizing its connections with matrix and tensor models, discrete gravity path integrals, and loop quantum gravity. Through these connections, GFTs emerge naturally as quantum field theories of "spacetime atoms". I will then discuss how semiclassical, macroscopic physics can emerge from GFT, touching upon the challenges of defining locality and coarse-graining in quantum gravity, and on how these can be naturally addressed within relational frameworks. I will present a concrete implementation of this relational strategy in GFT and show how a simple relational coarse-graining scheme can be used to extract cosmological physics. Within the resulting cosmological models, the initial singularity is resolved into a quantum bounce, while cosmological perturbations emerge from the quantum entanglement of the underlying quantum-gravity degrees of freedom, with effective dynamics modified on trans-Planckian scales. Finally, I will show that quantum-gravitational interactions alone can generate cosmic acceleration, leading both to dynamical dark energy and to a slow-roll inflationary phase. I will conclude by showing recent observational constraints on such emergent dynamical dark energy models, and by providing an outlook on future research directions.

会場: 研究本館 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