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Classical Spinning Black Hole Scattering from Quantum Amplitudes

2026年1月15日(木) 14:00 - 15:30

Dogan Akpinar (Ph.D. Student, Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh, UK)

Scattering amplitudes have recently become a powerful tool for extracting classical observables in two-body gravitational dynamics, with direct relevance for current and future gravitational-wave experiments. In this talk, I will review how quantum scattering amplitudes can be used to obtain classical black hole scattering observables. A key focus will be the inclusion of spin effects, modelled by treating black holes as point particles in fixed-spin representations. This approach introduces a subtle ambiguity in the separation between classical and quantum information, which we resolve using our spin interpolation method. Leveraging this, we obtain, for the first time, the classical two-loop amplitude accurate to quartic order in spin, from which we extract physical observables such as linear and angular impulses using covariant Dirac brackets. Remarkably, the resulting amplitude obeys a spin-shift symmetry, remaining invariant under a shift of the black hole spin by the momentum transfer in the scattering process. Motivated by this structure, we examine the conserved quantities governing scattering and show that—at least asymptotically—the probe dynamics remain integrable through quartic order in spin. Under this asymptotic integrability, together with the spin-shift symmetry, we demonstrate that the quartic-in-spin radial action is fully determined by the aligned-spin sector. Taken together, these results advance our understanding of spinning black hole scattering and illuminate new structural features of Kerr dynamics.

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

Invitation to Random Tensor Models: from random geometry, enumeration of tensor invariants, to characteristic polynomials

2026年1月6日(火) 13:30 - 14:30

鳥海 玲子 (沖縄科学技術大学院大学 (OIST) 准教授)

I will introduce random tensor models by first reviewing their motivation coming from random geometric approach to quantum gravity. Then, I will selectively present some of the interesting research results, by highlighting recent results on enumeration of graphs representing tensor invariants, and reporting our recent work on a new notion of characteristic polynomials for tensors via Grassmann integrals and distributions of roots of random tensors. The latter two are based on arXiv:2404.16404[hep-th] and arXiv:2510.04068[math-ph]

会場: 研究本館 3階 359号室 (メイン会場) / via Zoom

イベント公式言語: 英語

Neural Network Quantum States for Quarkonium in Medium: Real-Time Open Quantum-System Dynamics

2025年12月19日(金) 16:00 - 17:00

Tom Magorsch (Ph.D. Student, Department of Physics, Technical University of Munich, Germany)

Many phenomena in high energy physics can not be described by Euclidean-time Monte Carlo estimates alone, but require genuine real-time evolution and a treatment of non-equilibrium effects. However, such simulations are computationally challenging. One such example is the evolution of heavy quarkonium in the quark gluon plasma produced in heavy-ion collisions. In this talk, I will introduce the open quantum system treatment of in-medium quarkonium. I will then give an overview on neural network quantum states as a variational approach to the real-time simulation of open quantum systems. As a controlled benchmark system, I will study the application to the Caldeira-Leggett model and conclude with an outlook on future applications of neural network based simulation of quarkonia in medium.

会場: via Zoom

イベント公式言語: 英語

Phase transition in parametrized quantum circuits

2025年12月16日(火) 10:00 - 12:00

王 啸洋 (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 量子数理科学チーム 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

RIKEN Quantum hands-on seminar on IBM and QEDMA software for quantum computing beginners

2025年12月15日(月) 9:30 - 12:20

This seminar will be conducted in a hybrid format, both in-person and via Zoom. Since it includes hands-on sessions, we kindly ask you to consider attending in person whenever possible to ensure more effective learning. The overview of the seminar is as follows: Program: 9:30 - 10:50 Yuri Kobayashi (IBM Quantum) "Introduction to IBM Quantum and Qiskit" 10:50 - 11:00 Break 11:00 - 12:20 Ori Alberton (QEDMA) "Introduction to QESEM error mitigation software: Theory,  use-case demonstrations and usage tutorial" Abstract of Yuri Kobayashi's tutorial: This talk introduces HPC researchers to the IBM Quantum platform and the Qiskit SDK, providing a practical orientation to quantum programming without assuming prior quantum-computing knowledge. Attendees will learn how to construct and execute quantum circuits using Qiskit, explore available simulators, and real quantum backends and submit jobs to IBM’s cloud-based quantum processors. The session will also showcase how to map your problem to quantum circuits through specific use-case applications. Abstract of Ori Alberton's tutorial: This talk introduces QESEM, Qedma’s characterization-based software tool for reliable, high-accuracy quasi-probabilistic error mitigation. We will begin by explaining why error mitigation methods are expected to be the first to unlock quantum advantage, and why they will continue to play a central role even as error correction becomes feasible. We will highlight some of the key innovations underlying QESEM’s operation and present recent results on IBM Heron r2 devices demonstrating its capabilities in the largest utility-scale unbiased error mitigation experiment to date. In addition different use-cases and demonstrations ran by QESEM users will be presented. Finally, we will provide guidance on how to start using QESEM to obtain error-mitigated results in experiments on IBM quantum systems.

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

京都大学MACSプログラムスタディグループ 理研訪問・研究交流会 —理研研究者と語る最前線—

2025年12月12日(金) 12:30 - 15:10

12:00 – 13:30 コーヒーミーティング参加 13:30 – 14:10 入谷 亮介 (理研 iTHEMS 上級研究員) — 研究キーワード:数理生物学, 進化生態学 14:10 – 14:30 休憩 14:30 – 15:10 森川 億人 (理研 iTHEMS 基礎科学特別研究員) — 研究キーワード: 格子場の理論, 共形場理論, 場の量子論, 素粒子論

会場: 研究本館 3階 345-347室

イベント公式言語: 日本語

Graph polynomials and quantum field theory

2025年12月9日(火) 15:00 - 17:00

Michael McBreen (Assistant Professor, Department of Mathematics, The Institute of Mathematical Sciences, The Chinese University of Hong Kong, Hong Kong)

The Tutte polynomial was introduced in the 1940s as a two-variable generalisation of the chromatic polynomial of a graph. It is the universal matroid invariant satisfying a deletion-contraction relation, and is the subject of much recent work. I will describe a geometric realisation of the Tutte polynomial via the cohomology of a symplectic dual pair of hypertoric varieties. The same construction associates an interesting two-variable polynomial to any pair of symplectically dual spaces, whose one-variable specialisations recover the respective Poincare polynomials. Joint work with Ben Davison.

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

About analytic continuation of quantum field theories in non-integer dimensions

2025年12月5日(金) 14:00 - 15:30

Slava Rychkov (Professor, Institut des hautes études scientifiques, France)

Analytic continuation in dimension has been used first as a way to regularize perturbative quantum field theory. But since the work of Wilson and Fisher, quantum field theory in d-dimension has been used more radically, to connect theories living say, in d=4, to theories in d=3 and d=2. Mathematically it's not fully clear what this means. I will give some thoughts about this subject, and I will describe some recent paradoxes which arise when one consider expansion of O(N) models around d=2, based on recent work with Fabiana De Cesare.

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

The Functional Renormalisation Group: From the physics of strongly correlated systems to generative models

2025年12月5日(金) 10:30 - 12:00

Jan Martin Pawlowski (Professor, Institute for Theoretical Physics, University of Heidelberg, Germany)

In the past decades, the functional renormalisation group (fRG) has matured into a comprehensive approach to strongly-correlated (non-perturbative) systems, covering quantitatively both universal and non-universal phenomena. The fRG also constitutes an ideal approach for unravelling structural aspects of quantum field theories. This is not only interesting for studies in mathematical physics, but also guides systematic diagrammatic expansion schemes. It is also used to set up novel statistical (lattice) approaches to non-perturbative phenomena. In the present talk I survey these advances and illustrate the progress with selected examples ranging from ultracold atoms, QCD and quantum gravity to novel generative architectures for lattice simulations and beyond.

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

Quantum Information in Scattering: From Amplitude Poles to Entanglement Features

2025年12月4日(木) 14:00 - 16:00

蘇 俊文 (Postdoctoral Researcher, Department of Physics, Tsinghua University, Beijing, China)

Probing quantum entanglement in high-energy collisions has recently become a rapidly growing direction in particle physics, aiming to measure quantum correlations at the highest energy scales accessible to humans. A key question is how such entanglement relies on the analytic structure of scattering amplitudes. In this talk, I will show that the pole structure, associated with intermediate heavy particles, leads to distinctive entanglement features. When a heavy particle mediates inelastic scatterings with three or more final particles, the entanglement entropy between its decay products and the rest exhibits a universal dip as the energy increases, reflecting the limited information flow through on-shell heavy particles and signaling entanglement suppression in the heavy-particle-dominated regime. This reveals entanglement structures beyond the usual “area-law” behavior of 2-to-2 processes. Finally, I will comment on possible ways to probe these features experimentally through analyses of final-state phase-space distributions. This talk is based on JHEP 10 (2025) 003 [arXiv: 2507.03555].

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

Quantum Computing Journal Club #1

2025年12月2日(火) 10:00 - 12:00

Bring a recent paper on quantum computing for discussion. No need to prepare slides.

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

Hamiltonian Learning and Dynamics Prediction via Machine Learning

2025年11月26日(水) 15:00 - 16:00

李 可仁 (Assistant Professor, College of Physics and Optoelectronic Engineering, Shenzhen University, China)

Accurate prediction of quantum Hamiltonian dynamics and identification of Hamiltonian parameters are crucial for advancements in quantum simulations, error correction, and control protocols. This talk introduces a machine learning model with dual capabilities: it can deduce time-dependent Hamiltonian parameters from observed changes in local observables within quantum many-body systems, and it can predict the evolution of these observables based on Hamiltonian parameters. The model’s validity was confirmed through theoretical simulations across various scenarios and further validated by two experiments. Initially, the model was applied to a Nuclear Magnetic Resonance quantum computer, where it accurately predicted the dynamics of local observables. The model was then tested on a superconducting quantum computer with initially unknown Hamiltonian parameters, successfully inferring them. We believe that machine learning techniques hold great promise for enhancing a wide range of quantum computing tasks, including parameter estimation, noise characterization, feedback control, and quantum control optimization.

会場: via Zoom

イベント公式言語: 英語

9th QGG Intensive Lectures – Correlation Effects in Quantum Many-Body Systems: Some Prototypical Examples in Condensed Matter Physics

2025年11月19日(水) - 20日(木)

川上 則雄 (理化学研究所 最先端研究プラットフォーム連携 (TRIP) 事業本部 基礎量子科学研究プログラム 副プログラムディレクター)

The ninth installment of the Intensive Lecture Series, organized by the Quantum Gravity Gatherings (QGG) study group at RIKEN iTHEMS, will feature Prof. Norio Kawakami from the Fundamental Quantum Science Program (FQSP) under RIKEN's Transformative Research Innovative Platform (TRIP). Over the course of two days, Prof. Kawakami will deliver a lecture series on quantum many-body systems. In recent years, insights from quantum many-body physics have become central to research in quantum gravity, where correlation effects induced by gravity play nontrivial roles. By bridging perspectives from gravitational physics and quantum many-body dynamics, one hopes to understand how macroscopic spacetime and its geometric properties emerge from the collective behavior of quantum constituents at microscopic scales. In this lecture series, Prof. Kawakami will introduce the fundamental properties of correlation effects through representative examples in condensed matter physics. A distinctive aspect of this event is its joint organization with the Fundamental Quantum Science Program (FQSP) at RIKEN. The goal is to further strengthen connections between the quantum gravity, condensed matter, and quantum information communities. 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. Abstract: Some examples of theoretical methods to treat strongly correlated systems in condensed matter physics are explained. We start with the Kondo effect, which is one of the most fundamental quantum many-body problems and has been intensively studied to date in a wide variety of topics such as dilute magnetic alloys, heavy fermion systems, quantum dot systems, etc. Dynamical mean-field theory (DMFT) is then introduced, which enables us to systematically treat strongly correlated materials such as a Mott insulator. It is shown that the essence of DMFT is closely related to the Kondo effect. Furthermore, we explain how to apply conformal field theory (CFT) to treat correlation effects in one-dimensional electron systems.

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Chiral anomaly in Hamiltonian lattice gauge theory

2025年11月18日(火) 10:00 - 12:00

山本 新 (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 量子数理科学チーム 上級研究員)

The 4th quantum computing gathering organized by Quantum Computing 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

Mathematical Application Research Team Meeting #10

2025年11月14日(金) 16:00 - 17:00

緒方 芳子 (京都大学 数理解析研究所 (RIMS) 教授)

Mathematical Application Research Team invites Prof. Yoshiko Ogata from RIMS for this meeting. Her talk title will be announced later. You are welcome to join the meeting. The title and the abstract of her talk are: Title: Mixed state topological order: operator algebraic approach Abstract: We consider anyons in mixed states of two-dimensional quantum spin systems within the operator-algebraic framework of quantum statistical mechanics. To each state satisfying a mixed-state version of approximate Haag duality, we associate a braided C*-tensor category, which we interpret as describing the anyonic excitations of the state. We then investigate how these anyonic structures behave under interactions with the environment.

会場: セミナー室 (359号室) 3階 359号室 (メイン会場) / via Zoom

イベント公式言語: 英語

Pairing in Bose-Fermi and Fermi-Fermi systems

2025年11月6日(木) 15:00 - 16:30

Pierbiagio Pieri (Associate Professor, Dipartimento di Fisica e Astronomia “Augusto Righi”, Università di Bologna, Italy)

This seminar is co-hosted by GWX-EOS Working Group and iTHEMS-ABBL Joint Astro Study Group. Abstract: In the first part of my talk, I will review recent work on Bose-Fermi mixtures with an attractive interaction inducing pairing between bosons and fermions. After discussing a recent experiment on this system [1], which has confirmed predictions obtained by us some time ago within a many-body diagrammatic approach [2], I will present novel results for the compressibility [3] that suggest a metastable nature for the many-body phase observed in [1]. Then, I will discuss the extension of our calculations to two-dimensional Bose-Fermi mixtures [4,5]. The results obtained in 2D challenge previous beliefs formulated for 3D systems. In the second part, I will discuss attractive polarized Fermi systems, for which the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase was proposed many years ago as a possible superfluid phase. I will discuss how significant precursor FFLO fluctuation effects appear already in the normal phase of polarized Fermi gases at finite temperature [6], and how they could be experimentally detected with ultracold gases. At zero temperature [7], I will discuss how the quasi-particle parameters of the normal Fermi gas change when approaching an FFLO quantum critical point, with a complete breakdown of the quasi-particle picture analogous to what found in heavy-fermion materials at an antiferromagnetic quantum critical point. Finally, I will discuss a recent joint experimental-theoretical work on the motion of a vortex orbiting a pinned anti-vortex in a strongly interacting Fermi gas [8], highlighting the interplay between Andreev bound states in the vortex core and delocalized thermal excitations in shaping the vortex dynamics.

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

Quantum multi-body problems using unsupervised machine learning

2025年11月5日(水) 15:00 - 16:00

内藤 智也 (東京大学 大学院工学系研究科 原子核国際専攻 特任助教)

I will introduce the recent development of a method to calculate the (anti)symmetrized wave functions and energies of the ground and low-lying excited states using the unsupervised machine learning technique. I will also introduce the recent attempts to consider the spin-isospin degrees of freedom and extend them to the Dirac equation.

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

Operational Quantum Frames: from quantum mechanics to quantum field theory and beyond

2025年10月30日(木) 16:00 - 17:00

Jan Głowacki (Postdoc, Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Austria)

In this talk I will begin with a concise overview of the development of the operational approach to quantum reference frames (QRFs), tracing the line from its foundational contributions to its most recent applications. I will then introduce the central ideas of the research direction that I am pursuing which aims at developing relational foundations for relativistic quantum physics. The starting point is the application of the operational QRF formalism to the context of the Poincaré group, and establishing connections between this emerging framework and existing formalisms in quantum field theory. This part of the talk will summarize results from a recent preprint written with Samuel Fedida [1]. I will conclude by outlining a number of open research directions, highlighting selected topics in more detail depending on the available time and the interests of the audience

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

The 1st Joint General Meeting of RIKEN Quantum and the QII RIKEN User Group

2025年10月24日(金) 13:20 - 17:45

The joint general meeting is scheduled to be held at Okochi Hall from 13:20 to 17:45. The networking reception is scheduled to be held at the RIKEN Cafeteria from 18:00 to 19:40.

会場: 大河内記念ホール

イベント公式言語: 英語