Quantum Error Mitigation

2025年1月28日(火) - 29日(水)

遠藤 傑 (NTTコンピュータ&データサイエンス研究所 理論量子情報研究センタ 准特別研究員)

Note for registration [2024-12:24]: We are sorry that the number of registration has reached the capacity of the lecture room. Thank you for your understanding. Note for participants [2024-12:18]: For participants, please register from the above form. We may limit the number of participants due to the capacity of the lecture room. For participants in RIKEN who have already answered a questionnaire on this lecture, you do not have to register. Program: Day 1 (Jan. 28th) 10:30-12:00 Lecture 1 12:00-13:30 Lunch time 13:30-15:00 Lecture 2 15:00-15:30 Coffee break 15:30-17:00 Lecture 3 Day 2 (Jan. 29th) 10:30-12:00 Lecture 4 12:00-13:30 Lunch time 13:30-15:00 Lecture 5 15:00-15:30 Coffee break 15:30-17:00 Lecture 6 Abstract: Quantum Error Mitigation (QEM) offers a practical approach to reducing errors in noisy intermediate-scale quantum (NISQ) devices without requiring the encoding of qubits. In this seminar, I will begin by discussing the fundamentals of noise modeling in quantum systems, followed by an overview of QEM techniques, including extrapolation, probabilistic error cancellation (PEC), virtual distillation, quantum subspace expansion, and Clifford data regression. Next, I will present advanced QEM methods, such as the stochastic PEC approach, which mitigates the effects of Lindblad terms in Lindblad master equations and the generalized quantum subspace expansion, which is a unified framework of QEM. I will also explore recent research on the information-theoretic analysis of QEM, shedding light on its fundamental limits and connections to non-Markovian dynamics. Furthermore, I will discuss studies combining QEM with quantum error correction to enhance the reliability of computations in the early fault-tolerant quantum computing era. Lastly, I will highlight the relevance of hybrid tensor networks, particularly their connections to quantum subspace expansion techniques.

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Reheating after a cosmological constant relaxation and gravitational waves lensed by a supermassive black hole

2025年1月30日(木) 14:00 - 15:30

Paul Martens (Postdoctoral Fellow, Department of Physics, The Chinese University of Hong Kong, China)

This presentation will be articulated in two parts. In a first part, I will present the a reheating mechanism that follows a dynamically relaxed cosmological constant. The latter is achieved by the dynamics of a scalar field whose kinetic term is modulated by an inverse power of spacetime curvature. While it is at work against radiative corrections to the dark energy, this process alone would wipe out not only the vacuum energy, but also all other matter contents. A reheating phase is thus introduced, which exploits a null-energy-condition violating sector. In a second part, I shall present a more recent and still ongoing project to describe and characterize the lensing of gravitational waves by an active galactic nuclei (or any supermassive black hole), in the geometric limit. Such systems are simple enough for constraints to be derived with only few assumptions. Yet, they present interesting features that could provide information on e.g. on binary black hole formation mechanisms and quasinormal modes.

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

Effective size and dimension, in biology and beyond

2025年1月30日(木) 16:00 - 17:00

入谷 亮介 (数理創造プログラム 上級研究員)

This talk will be a very short, introductory talk on some fundamental concepts of “effective size” from population-biological, statistical, and mathematical viewpoints.

会場: via Zoom

イベント公式言語: 英語

D-modules and the Riemann-Hilbert correspondence as a foundation for mixed Hodge modules

2025年1月31日(金) 14:00 - 16:00

齋藤 隆大 (中央大学 理工学部 助教)

Algebraic analysis is a field which began with the study of differential equations in an algebraic framework, known as D-modules. The Riemann-Hilbert correspondence lies at the heart of this field, which bridges the worlds of analysis and geometry. Thanks to this, some geometric problems can be studied by using D-module theory, and vice versa. Based on D-module theory, Morihiko Saito introduced the concept of mixed Hodge modules, realizing Hodge theory on constructible sheaves, which brings us a functorial treatment of Hodge theory and various applications. In this talk, we will begin with the linear differential equations on the complex plane and introduce monodromy, regularity and Deligne's Riemann-Hilbert correspondence. Then, as a generalization of it, I will explain the basics of the theory of D-modules and the Riemann-Hilbert correspondence. Finally, I will describe the role they play in the theory of Hodge modules and recent progress in this area. For the audience's background knowledge, I will assume basic complex function theory. I will start with a simple example, so people outside the field are welcome.

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

Introduction to the stochastic process and its application in physics

2025年2月4日(火) - 5日(水)

金澤 輝代士 (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 准教授)

The stochastic process is a popular tool for broad disciplines, such as physics, biophysics, chemistry, neuroscience, economics, and finance. In this lecture course, I will provide an elementary introduction to stochastic processes in physics without assuming rigorous background knowledge of probability theories. Most of the basic topics in stochastic processes will be covered in this lecture course, such as (1) the one-to-one correspondence between stochastic differential equations and master equations, (2) their standard forms, (3) Ito's lemma, and (4) the perturbation theories (the system-size expansion). I will also present its application to statistical physics, such as (5) kinetic theory and (6) a microscopic derivation of the Langevin equation from hard-sphere Hamiltonian dynamics in the dilute gas limit. My goal is to help the audience calculate most of the main calculations by their own hands by providing detailed explanations without abbreviations. This lecture is based on my Japanese notebook, available on my webpage (see the link below). Schedule: (Tue., Feb. 4) 13:00-14:30, 14:45-16:15, 16:30-18:00 (Wed., Feb. 5) 10:30-12:00, 13:00-14:30, 14:45-16:15

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

Master equations for general non-Markovian processes: the Hawkes process and beyond

2025年2月5日(水) 16:30 - 18:00

金澤 輝代士 (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 准教授)

The Markovian process is one of the most important classes of stochastic processes. The Markovian process is defined as a stochastic process whose time evolution is independent of the system's entire history and has been extensively studied using the master equation and Fokker-Planck equation approaches. In contrast, non-Markovian processes -- where time evolution depends on the full history of the system -- have not been systematically explored, except for a few special cases, such as semi-Markovian processes. In this talk, we present a recent master-equation approach to general non-Markovian jump processes [1-4]. Beginning with a general non-Markovian jump process, we derive the corresponding master equation through a Markovian-embedding approach. The Markovian embedding is a scheme to add a sufficient number of auxiliary variables to convert a non-Markovian model to a high-dimensional Markovian model. For the case of our model, the one-dimensional non-Markovian model is shown to be equivalent to a Markovian stochastic field theory, and we derive the field master equation correspondingly [4]. As an application, we examine the nonlinear Hawkes process, a history-dependent and self-exciting model frequently used in studying complex systems [1-3]. Additionally, we explore the stochastic thermodynamic framework for general jump processes [5] as another example.

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

Mathematics of the Future, Science of the Future: Large Language Models and Their Applications

2025年2月6日(木) 14:00 - 16:00

三内 顕義 (京都大学 大学院理学研究科 特定准教授)

In recent years, the rapid development of large language models (LLMs) such as ChatGPT has given many researchers a strong impression that these systems truly exhibit “intelligence.” In this presentation, we first review the evolution of AI research, explaining how large language models go beyond conventional machine learning by enabling more “general” forms of learning. We then highlight the importance of “sensors” and “mathematical capability” as key factors that allow AI to autonomously carry out scientific tasks such as problem analysis, hypothesis generation, and proofs in fields like mathematics and physics. We also examine how proof assistants can address the issue of hallucinations in LLM outputs, and discuss the role of combinatorial creativity in accelerating interdisciplinary research. Finally, we introduce our “AI Mathematician” agent project, demonstrating how integrating large language models with proof assistants can open new horizons in mathematical sciences.

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

A coarse-grained model of disordered RNA for simulations of biomolecular condensates

2025年2月6日(木) 16:00 - 17:00

安田 一希 (慶應義塾大学 大学院理工学研究科 博士課程)

Protein-RNA condensates are involved in a range of cellular activities. Coarse-grained molecular models of intrinsically disordered proteins have been developed to shed light on and predict single-chain properties and phase separation. An RNA model compatible with such models for disordered proteins would enable the study of complex biomolecular mixtures involving RNA. Here, we present a sequence-independent coarse-grained, two-bead-per-nucleotide model of disordered, flexible RNA based on a hydropathy scale. We parameterize the model, which we term CALVADOS-RNA, using a combination of bottom-up and top-down approaches to reproduce local RNA geometry and intramolecular interactions based on atomistic simulations and in vitro experiments. The model semi-quantitatively captures several aspects of RNA-RNA and RNA-protein interactions. We examined RNA-RNA interactions by comparing calculated and experimental virial coefficients, and non-specific RNA-protein interaction by studying reentrant phase behavior of protein-RNA mixtures. We demonstrate the utility of the model by simulating the formation of mixed condensates consisting of the disordered region of MED1 and RNA chains, and the selective partitioning of disordered regions from transcription factors into these, and compare the results to experiments. Despite the simplicity of our model we show that it captures several key aspects of protein-RNA interactions and may therefore be used as a baseline model to study several aspects of the biophysics and biology of protein-RNA condensates.

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

Fireworks in the cosmos: The Hidden Power of Nuclear Reactions

2025年2月7日(金) 14:00 - 15:15

Irin Sultana (Ph.D. Student, Department of Physics, Central Michigan University, USA)

Neutron stars in low-mass X-ray binaries, accreting hydrogen- or helium-rich material from a companion star, frequently exhibit thermonuclear runaways on their surfaces known as Type-I X-ray bursts (XRBs). These bursts are powered by nuclear processes, such as the triple-$\alpha$ process, the $\alpha p$ process, and the rapid proton capture process, which play a critical role in model-observation comparisons. In this study, we investigate the impact of nuclear reaction uncertainties on XRBs using the ONEZONE model (Cyburt et al., 2016), considering different accreted compositions and accretion rates for the binary systems that are within the range of observed burst sources. The study is carried out in two stages. First, we determine the burst ignition conditions by simulating the settling of the accreted material with a full reaction network and a semi-analytical model. Second, we perform a sensitivity analysis by varying proton- and alpha-induced reaction rates in JINA REACLIBV2.2 within their estimated uncertainties. We explore the influence of these reactions on the XRBs light curve and the final abundances. The findings highlight key nuclear reactions that significantly affect XRB observables and the final abundances produced, offering guidance for future experimental efforts to improve our understanding of the uncertainties in the reaction rates involved in XRBs.

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

Investigating the Crust Urca Process in Accretion Neutron Stars: Implications for Superburst Ignition and Hot Cooling Curve of MAXI J0556-332

2025年2月7日(金) 16:00 - 17:15

Hao Huang (Ph.D. Student, Institute of Modern Physics, China)

This seminar investigates the Urca cooling strength of the 63Fe-63Mn pair, which varies due to uncertainties in the spin-parity of 63Fe, relevant to the Island of Inversion at N = 40. We present simulations that analyze the impact of this cooling mechanism on the thermal evolution of neutron star crusts, focusing on superburst ignition and anomalous hot quiescent phase cooling of MAXI J0556-332. Additionally, we explore the potential crust Urca process through the anomalous cooling curve of MAXI J0556-332, fitting observational data to determine neutron star mass and radius preferences. Preliminary results suggest that neutron stars with a crust Urca process tend to have smaller masses and larger radii, highlighting the need for precise β-decay measurements to further understand these phenomena.

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

Pebbles in Planet Formation

2025年2月10日(月) - 13日(木)

Research on planet formation involves various approaches, including explorations of small solar system bodies, observations of protoplanetary disks, dust experiments, simulations, and theoretical studies. One of the primary objectives in this field is to develop a comprehensive theory that explains how kilometer-sized planetesimals form from micrometer-sized dust grains, drawing upon findings from these diverse research methods. This workshop will focus on the concept of pebbles, which play a crucial role in the planet formation process. Pebbles — typically defined as solids ranging from millimeter to centimeter in size — are intermediate building blocks in planet formation, though their definition varies depending on the context. Assuming pebbles has led to theoretical advances in mechanisms such as streaming instability and pebble accretion, which promote the formation and growth of planetesimals. Additionally, pebbles have been linked to barriers against dust growth, such as the bouncing barrier. Furthermore, observations of protoplanetary disks have revealed the size distribution and porosity of solids, while the strength and thermal conductivity of comets obtained by the Rosetta mission suggest the accumulation of pebbles due to disk instabilities. However, inconsistencies have been pointed out between pebble formation and theories of dust growth. This workshop aims to revisit and refine our understanding of solid materials implicated in planet formation, particularly in light of findings from solar system explorations and protoplanetary disk observations. We aim to reevaluate the definition and role of pebbles in the broader context of planet formation, with a special focus on the current challenges and open questions in the field. The workshop will include discussions of experiments and simulations of dust growth and collisions, and planetesimal formation mechanisms such as streaming instability. The workshop features keynote talks from the perspectives of explorations, observations, experiments, simulations, and theories, and we also call for presentations on related topics.

会場: 国立天文台三鷹キャンパス (メイン会場) / via Zoom

イベント公式言語: 英語

MACS10周年記念コロキウム・2024年度MACS成果報告会

2025年2月19日(水) 14:45 - 18:30

國府 寛司 (京都大学 理事)
高橋 淑子 (京都大学 大学院理学研究科 生物科学専攻 教授)

14:45-15:00 ティータイムディスカッション [15:00-16:30 第1部 MACS10周年記念コロキウム] 15:05-15:05 はじめに（佐々真一 SACRA学際融合部門長） 15:05-15:30 講演1「MACS はどのように始まったか？」國府寛司 博士 （数学・数理解析専攻 教授） 2016年5月のキックオフシンポジウムから始まったMACSが2025年度で10年目を迎えるという時期にあたり，その立ち上げの時のことを振り返ってお話したい．特に，10年前にどのような人々がどのようなことを考えて，それがMACSプログラムに至ったのか，また当初MACSでやりたいと思っていたができなかったことなどを思い出し，この10年のMACSの歩みや，MACSとその後の京大理学の諸活動との関わりなどについて，いくつか取り上げてお話してみたい． 15:30-15:55 講演2「MACSから生まれた躍動感」高橋淑子 博士 （生物科学専攻 教授） 「MACS」は語呂がよかったせいか多くの人に覚えていただき、「名付け親」として嬉しい限りです。私はベタベタの実験発生生物学者であり数学とは縁遠かったのですが、なぜかMACSには初めから首を突っ込む形となり、以来、10年間にわたりSGを企画しました。「本物（トリ胚）をみて数理を考える」という共通テーマのもと、物理・数学の院生や学部生たちが数式を議論し、顕微鏡をのぞいて生（なま）のトリ胚を観る姿に心躍りました。当時ハーバード大から出た「腸ルーピング」論文は、実験生物―物理―数理の融合研究で世の中を驚愕させましたが、「ハーバードでできることが京大理学でできないはずがない」を合い言葉に、新しい挑戦に胸躍る10年間でした。 15:55-16:20 質疑応答 16:20-16:30 休憩 [16:30-18:30 第2部 2024年度 MACS 成果報告会] 16:30-17:30 各スタディグルーブ フラッシュトーク 17:30-18:30 参加学生によるポスター発表

会場: 京都大学 理学研究科セミナーハウス（建物配置図（北部構内）【10】の建物）

イベント公式言語: 日本語

How to define a Majorana fermion?

2025年2月20日(木) 13:00 - 14:30

藤川 和男 (東京大学 名誉教授)

It is fundamental in particle physics if the neutrino is a Dirac fermion or a Majorana fermion, and the seesaw model gives naturally a Majorana neutrino in an extension of the Standard Model. However, the commonly used chirality changing \(pseudo-C symmetry \) \(\nu^{\tilde C}_L=C\overline{\nu_L}^T\) of a chiral fermion is not defined in Lagrangian field theory. Precisely speaking, the neutrinoless double beta decay is not described by the pseudo-C symmetry. The Majorana neutrino obtained after a Bogoliubov-type canonical transformation, which is the one originally defined by Majorana using a Dirac-type fermion, describes consistently all the properties expected for the Majorana neutrino. Physical implication of this fact is briefly discussed.

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

iTHEMS Cosmology Forum 3 - (P)reheating the primordial Universe

2025年3月4日(火) 9:30 - 17:35

榎本 成志 (横浜国立大学 理工学部 博士研究員)
John T. Giblin (Professor, Department of Physics, Kenyon College, USA)
向田 享平 (高エネルギー加速器研究機構 (KEK) 理論センター 助教)

iTHEMS Cosmology Forum Workshop is a series of short workshops, each focusing on an emerging topics in cosmology. The target audience is cosmologists, high-energy physicists and astronomers interested in learning about the subject, not just those who have already worked on the topic. The goal of the workshop is to provide working knowledge of the topic and leave dedicated time for discussions to encourage mutual interactions among participants. The third workshop is devoted to the 'reheating' phase of the early Universe. Reheating bridges the gap between the (almost) empty universe at the end of cosmic inflation and the thermal state of particles, required for Big-Bang nucleosynthesis, and the events of the hot Big-Bang model as a whole, to unfold. It is expected to proceed in different stages starting with a violent parametric resonant creation of particles, dubbed preheating, followed by a redistribution of energy leading to a thermal state. This phase potentially hosts rich phenomenology such as the formation of topoligical defects e.g. solitons, generation of gravitiational wave, and so on. Yet, the very non-linear nature of reheating makes it notoriously hard to describe analytically, and even numerical simulations struggle to follow the whole sequence of events in a given model. Reheating studies have thus yet to reach the degree of compherensiveness and universality that the understanding of cosmic inflation has achieved. This forum will consist of two events. The first, on March 4th, will be in conference format comprising scientific talks on research trends in (P)Reheating. The second, on March 5th, will be a tutorial on numerical aspects of reheating (both theory and hands-on with code) hosted by Tom Giblin of Kenyon College. The workshop will be in English. The workshops are organised by the iTHEMS Cosmology Forum working group, which is the successor of the Dark Matter Working Group at RIKEN iTHEMS. Important dates: Feb. 25th - Registration deadline March 4th - Workshop Day March 5th - Tutorial Day Invited Speakers: John T. Giblin - Kenyon College Kyohei Mukaida - KEK Seishi Enomoto - Yokohama National University Organisers: Kohei Hayashi, Nagisa Hiroshima, Derek Inman, Amaury Micheli, Ryo Namba

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Smart heuristics of a single-celled organism

2025年3月7日(金) 14:00 - 15:30

中垣 俊之 (北海道大学 電子科学研究所 教授)

Although we rarely question how smart unicellular organisms are, it has become clear that unicellular organisms are smarter than we expected. In fact, various protozoa (unicellular eukaryotes) can take actions that are advantageous for their survival even in complex environments in the wild environments. In this talk, I will introduce some typical examples of smart behaviors in a protozoan amoeba (the plasmodium of Physarum polycephalum): (1) maze-solving, (2) formation of multi-functional transport network that mimics public transportation network among cities in Tokyo region, and so on. We will propose a mathematical model of these behaviors and extract the heuristics (simple rules of behavior) that give rise to their smartness. In general, we will discuss the future potential of research into the behavioral intelligence of protozoa.

会場: 大河内記念ホール (メイン会場) / via Zoom

イベント公式言語: 英語

Third Workshop on Density Functional Theory: Fundamentals, Developments, and Applications (DFT2025)

2025年3月25日(火) - 27日(木)

The density functional theory (DFT) is one of the powerful methods to solve quantum many-body problems, which, in principle, gives the exact energy and density of the ground state. The accuracy of DFT is, in practice, determined by the accuracy of an energy density functional (EDF) since the exact EDF is still unknown. Currently, DFT has been used in many communities, including nuclear physics, quantum chemistry, and condensed matter physics, while the fundamental study of DFT, such as the first principle derivations of an accurate EDF and methods to calculate many observables from obtained densities and excited states, is still ongoing. However, there has been little opportunity to have interdisciplinary communication. On December 2022, we had the first workshop on this series (DFT2022) at Yukawa Institute for Theoretical Physics, Kyoto University, and several interdisciplinary discussions and collaborations were started. On February 2024, we had the second workshop on this series (DFT2024) at RIKEN Kobe Campus, and more stimulated discussion occured. To keep and extend collaborations, we organize the third workshop. Since the third workshop, we extend the scope of the workshop to the development and application of DFT as well. In this workshop, the current status and issues of each discipline will be shared towards solving these problems by meeting together among researchers in mathematics, nuclear physics, quantum chemistry, and condensed matter physics. This workshop mainly comprises lectures/seminars on cutting-edge topics and discussion, while sessions composed of contributed talks are also planned.

会場: 融合連携イノベーション推進棟（IIB） 8階 / via Zoom

イベント公式言語: 英語