高温超导体、光场调控、kagome金属 | 本周物理讲座

1

报告人：向涛，中国科学院物理研究所

时间：11月8日（周五）9:30

单位：中国科学院物理研究所

地点：M234会议室

摘要：

The discovery of high-temperature superconductivity has sparked numerous breakthroughs in physics, generated high expectations for practical applications, and posed substantial challenges to quantum theory. In this talk, I will clarify the nature of the high-temperature superconductivity problem and argue that its resolution could not only solve the mystery of high-temperature superconductivity itself, but also lead to the formulation of a comprehensive non-perturbative quantum theory.

报告人简介：

向涛，1984年在清华大学获学士学位。1986年在清华大学获硕士学位。1990年在中国科学院理论物理研究所获博士学位。1990-98年先后在英国牛津大学、Warwick大学和剑桥大学做博士后研究工作。1998年中国科学院理论物理研究所研究员。2007年中国科学院物理研究所研究员。北京量子信息科学研究院院长，中国科学院院士，发展中国家科学院院士，“中国物理快报”主编。从事凝聚态物理理论研究，主要包括高温超导机理、密度矩阵与张量重正化群、Mott绝缘体及量子自旋液体等。

2

报告人：孙麓岩，清华大学

时间：11月6日（周三）15:10

单位：北京大学物理学院

地点：物理楼中楼212

摘要：

Quantum information is vulnerable to environmental noise and experimental imperfections, which can impede the reliability of practical quantum information processors. As a result, quantum error correction (QEC) is essential for protecting quantum information against noise, making it crucial for universal and scalable quantum computation. Bosonic modes, with their infinitely large Hilbert space, enable redundant information encoding, making them a hardware-efficient solution for QEC. In this talk, I will discuss the fundamentals of QEC, highlight the advantages of QEC based on bosonic codes, and present the latest experimental advancements in this field.

报告人简介：

Dr. Luyan Sun earned his bachelor’s degree from the Department of Physics at Zhejiang University. He then pursued his PhD at the University of Maryland, College Park, focusing primarily on silicon-based quantum computation. After obtaining his PhD, he moved to Yale University to work on quantum computation based on superconducting circuits as a postdoctoral researcher. Since 2013, Dr. Sun has been at the Institute for Interdisciplinary Information Sciences at Tsinghua University, where he leads his own lab dedicated to superconducting quantum computation. His research interests include quantum feedback, quantum error correction, quantum control, and quantum metrology. In 2019, Dr. Sun was selected to the National Science Fund for Distinguished Young Scholars.

3

报告人：于晓东，山东大学

时间：11月7日（周四）10:00

单位：中国科学院理论物理所

腾讯会议：708-620-617

摘要：

The mathematical theory of optimization has become a vital tool in various branches of science. Especially, the so-called semidefinite programs (SDPs) as a special instance of convex optimization problems have found widespread applications in quantum information. In many applications, however, one cannot directly formulate an SDP, as some intractable rank constraints remain on the occurring matrices. In this talk, we establish a link between rank-constrained optimization and the theory of quantum entanglement. More precisely, we prove that a large class of rank-constrained semidefinite programs can be written as a convex optimization over separable quantum states and, consequently, we construct a complete hierarchy of semidefinite programs for solving the original problem. This hierarchy not only provides a sequence of certified bounds for the rank-constrained optimization problem, but also gives pretty good and often exact values in practice when the lowest level of the hierarchy is considered. We demonstrate that our approach can be used for relevant problems in quantum information processing, such as the quantum marginal problem, the existence of absolutely maximally entangled states, the optimization over pure states, the characterization of faithful entanglement, and the dimension witness of quantum systems.

报告人简介：

于晓东，山东大学物理学院教授，博士生导师。2017年在山东大学获得理论物理博士学位，2017-2021年在德国锡根大学进行博士后研究，2021年10月受聘回到山东大学工作，先后入选山东大学齐鲁青年学者（第一层次）、山东省泰山学者青年专家、国家海外高层次青年人才。主要从事量子物理与量子信息的基础理论研究，在国际一流专业刊物发表论文30余篇，其中Phys. Rev. Lett. 论文7篇、Nat. Commun.论文1篇。

4

报告人：Nicolas Martin，斯特拉斯堡天文台

时间：11月7日（周四）14:00

单位：北京大学物理学院

地点：KIAA-Auditorium

摘要：

The oldest stars of our Galaxy, the Milky Way, are messagers from the very early times. I will show how we can use the combined power of detailed astrometric, photometric, and spectroscopic observations of our surroundings to constrain the formation of the first stellar structures and the first galaxies.

报告人简介：

Dr. Nicolas Martin is a tenured CNRS researcher at the Strasbourg astronomical Observatory. He obtained his PhD from the Strasbourg University in France in 2006. He then worked as a postdoctoral fellow at the Max Plank Institute for Astronomy in Heidelberg before joining the CNRS in 2012. He specializes in observations of dwarf galaxies and stellar streams in the Milky Way and Andromeda to understand galaxy formation. Dr. Martin was a member of the CFHT Science Council from 2016 to 2021 and was the Chair of the CFHT French Time Allocation Committee. He was the head of the Pan-STARRS1 Local Group Key Project and is now the leader of the Pristine survey that combines more than 300 nights of telescope time. He has published more than 260 papers with ~18,000 citations (h-index 66) including 4 Nature papers (1 as first author).

5

报告人：Yan Gong，紫金山天文台

时间：11月7日（周四）16:00

单位：北京大学物理学院

地点：KIAA-Auditorium

摘要：

The interstellar medium (ISM) is the engine driving the cosmic cycle, playing a pivotal role in star formation, stellar evolution, and feedback from supernova remnants. Understanding these processes is key to unraveling the broader evolution of galaxies. In this talk, I will present recent advancements from several studies, shedding light on different stages of the ISM and its impact on galactic ecosystems. First, I will highlight the latest results from the GLOSTAR survey, a comprehensive radio study that uncovers new details about massive star formation and the discovery of supernova remnants in our Galaxy. Next, I will delve into the molecular chemistry of HCNH+, examining its behavior across diverse environments. As a diagnostic tool, HCNH+ provides valuable insights into the early stages of molecular cloud evolution and the effects of feedback from star formation. Finally, I will explore the systematic identification of masers in carbon-rich AGB stars, revealing dichroic masers in circumstellar envelopes of AGB stars. These masers offer a unique window into the later stages of stellar evolution, potentially leading to new insights into stellar physics and evolution. By connecting these topics, this talk aims to provide new facets on the ISM, from the birth of stars to the intricate chemistry of molecular clouds and the final stages of stellar evolution.

报告人简介：

Yan Gong got his PhD from Purple Mountain Observatory in 2016. Following his PhD, he joined Max-Planck-Institute for Radio Astronomy as a postdoctoral researcher from 2017 to 2021, and then continued there as a scientific staff member from 2021 to 2023. Starting in 2024, he has been serving as a guest scientist at both Purple Mountain Observatory and Max-Planck-Institute for Radio Astronomy. His research focuses on molecular clouds, star formation, astrochemistry, circumstellar envelopes of late-type stars, and astronomical masers.

6

报告人：刘运全，北京大学

时间：11月7日（周四）16:00

单位：清华大学物理系

地点：理学院郑裕彤大讲堂

摘要：

超快激光是研究物质电子动力学研究的重要工具。报告将介绍课题组在超快光场调控和强场物理方面的一些进展，包括对超快激光光场的振幅、位相、偏振、轨道角动量、自旋角动量等调控，以及基于光场调控对强场物理重要过程如阈上电离、隧道电离以及高次谐波等的超快调控研究，并介绍新型阿秒钟在量子隧穿、电子自旋轨道耦合以及光场自旋轨道耦合等研究中的应用。

报告人简介：

刘运全，北京大学博雅特聘教授，2006年中国科学院物理所获博士学位，2006－2008年在马克思-普朗克核物理所做博士后研究，2009年入职北京大学，2011年获国家级人才基金支持，2014年获聘教育部特聘教授，入选科技部中青年科技创新人才计划，2015入选第二批中组部人才计划。曾获王选青年学者奖、饶毓泰基础光学奖、王大珩中青年光学奖、饶毓泰物理奖、叶企孙师表奖等，主要从事超快光学和超快物理方面研究。

7

报告人：Gabriel Aeppli，Paul Scherrer Institute, Switzerland

时间：11月8日（周五）16:00

单位：清华大学物理系

地点：物理楼（附中南侧）W101

摘要：

There are long-standing ideas and experiments concerning the emergence of unconventional quasiparticles in strongly interacting Fermi systems. The most dramatic are the fractional states originally observed for the two-dimensional electron gases in semiconductor heterostructures subjected to perpendicular magnetic fields, and explained shortly thereafter by Laughlin. Others found in zero field are more subtle in the sense that their peculiarity is reflected in their scattering rates which rise linearly together with their energies; these are the "marginal" fermions first conjectured for the layered cuprates also displaying high temperature superconductivity. Here we describe experiments revealing signatures of both types of anomalous quasiparticles in zero applied field. The material is Fe3Sn2, a ferromagnetic “kagome” metal, with numerous Weyl nodes near the Fermi level, and a high Curie temperature of ca. 640K. We investigated the compound using microfocused, laser-based angle-resolved photoemission, together with density functional theory (DFT) and machine learning- based analysis of images. Inelastic X-ray scattering measurements reveal that the correct starting point for understanding this material is not a single kagome layer, but rather a triangular lattice of Fe octahedra.Refs.

报告人简介：

Gabriel Aeppli是苏黎世联邦理工学院（ETH Zürich）和洛桑联邦理工学院（EPF Lausanne）的物理学教授，同时担任保罗谢勒研究所（Paul Scherrer Institute）光子科学中心的负责人。他所有学位均来自麻省理工学院（MIT），包括数学和电气工程的学士学位，以及电气工程的硕士和博士学位。他在IBM、贝尔实验室和NEC工作过，研究领域涵盖从液晶到磁性数据存储的问题。随后，他成为伦敦纳米技术中心的联合创始人兼主任，并担任伦敦大学学院的奎恩教授。此外，他还共同创立了生物纳米咨询公司，目前仍担任该公司的非执行董事。他频繁为全球多个从事科学与技术资金、评估和管理的机构提供顾问服务。他获得的荣誉包括英国物理学会的莫特奖（Mott Prize）、美国物理学会的奥利弗·巴克利奖（Oliver Buckley Prize）、国际纯粹与应用物理联合会的尼尔奖章/国际磁学奖（Néel Medal/International Magnetism Prize），并当选为美国艺术与科学院院士、美国国家科学院院士以及英国皇家学会院士。

8

报告人：Dmitry Kazakov，Joint Institute for Nuclear Research

时间：11月11日（下周一）10:00

单位：中国科学院理论物理所

地点：北楼五楼CCAST502报告厅

摘要：

We demonstrate how one can deal with non-renormalizable interactions despite the fact that completetreatment of such theories is absent. Within perturbation theory we sum up the leading diagrams using the generalization of the renormalization group equations. In particular, we consider the four-pointon-shell scattering amplitudes in D=6,8,10 supersymmetric Yang-Mills theory in the planar limit withinthe spinor-helicity and on shell supersymmetric formalism.We study the UV divergences and demonstrate how one can sum them over in all orders of PT. Analyzing the R-operation we obtain the recursive relations and derive the differential equations that sum the leading divergences in all loops generalizingthe standard RG formalism for the case of nonrenormalizable interactions. Solving the obtained RGequations for particular sets of diagrams analytically and for the general case numerically we analyze their high energy behaviour of the scattering amplitudes. We derive also the RG equation for the effective potential in the leading log approximation which is valid for an arbitrary scalar field theory in four dimensions. The solution to this equation sums up the leading logφ contributions to all orders of perturbation theory just like it takes place in renormalizable case. Application of this formalism to the co-called alpha-attractors in inflationary cosmology leads to increase of the potential at the minimum which can be interpreted as appearance of the cosmological constant due to quantum corrections.

报告人简介：

Dmitry Kazakov graduated from Moscow State University at 1974, got his PhD at the Bogoliubov Lab-oratory of Theoretical Physics of the Joint Institute for Nuclear Research(Dubna) at 1977and degree of Doctor of Science in Physics and Mathematics at 1988. Since then employed by JINR, now he is the Director of the Bogoliubov Laboratory of Theoretical Physics. He is a well known specialist in quantum field theory and high energy physics. Main papers are on multiloop calculations in QFT,renormalization theory, renormalization group, supersymmetric field theories, SUSY and collider phenomenology. He is a Professor and a Head of the chair at Moscow Institute of Physics and Technology (TechnicalUniversity), gave lectures on particle physics and quantum field theory at Moscow State University, Karlsruhe University(Germany), Lyon University (France), European Schools on high energy physics, JINR and ITEP schools of physics, etc. He is a Corresponding member of Russian Academy of Sciences, Editor-in chief of the journal Theoretical and Mathematical Physics.

9

报告人：Viktor Braguta，Joint Institute for Nuclear Research

时间：11月11日（下周一）14:30

单位：中国科学院理论物理所

地点：北楼五楼CCAST502报告厅

摘要：

In this report the influence of relativistic rotation on QCD properties will be considered. I am going to review the results which were obtained within lattice simulation of QCD. It has become commonplace to perform such studies in the reference frame rotating with the system under investigation. In this case there appears the gravitational field and the problem is reduced to study of QCD in this external gravitational field. In this report the following topics will be reviewed. The influence of relativistic rotation on the QCD critical temperatures. Equation of state of rotating QCD and the moment of inertia of quark-gluon plasma. Inhomogeneous phase transitions in rotating quark-gluon plasma.

报告人简介：

Viktor Braguta defended his Ph.D. thesis at the Moscow Institute for Physics and Technology(Moscow) in 2004. The same year he got a postdoctoral position at the Institute for High Energy Physics(Protvino, Moscow region). From 2016 to 2020 he was the head of the laboratory of lattice gauge theories at the Institute for Theoretical and Experimental Physics(Moscow). From 2020 until now the head of sector of hadronic matter under extreme conditions at the Bogoliubov Laboratory of Theoretical Physics of Joint Institute for Nuclear Research(Dubna, Moscow region). In addition he is a professor of Moscow Institute for Physics and Technology and professor of Russian Academy of Sciences.

10

报告人：周龙文，中国海洋大学

时间：11月11日（下周一）15:00

单位：中国科学院理论物理所

地点：北楼202

摘要：

Periodically driven (Floquet) systems have attracted growing attention due to the emergence of intriguing phenomena that are absent in equilibrium physics. In this talk, I will present a new class of Floquet criticality discovered in our recent work. For generic driven Majorana fermion chains with chiral symmetry, we analytically demonstrate that Floquet driving can enrich the transition point, resulting in topologically distinct quantum critical lines that are absent in undriven systems. Furthermore, we provide an intuitive physical explanation for the underlying mechanism of the nontrivial topology at Floquet criticality and generalize our results to higher dimensions. This work not only extends the scope of topological physics in Floquet systems but also deepens our understanding of gapless topological phases of matter.

报告人简介：

周龙文，中国海洋大学教授，博士生导师。主要研究领域为驱动量子体系的拓扑、纠缠与动力学特征。在Floquet拓扑态、非厄米拓扑态、动力学量子相变、纠缠相变等研究方向取得多项进展，发表SCI论文50余篇，现主持国家自然科学基金面上项目一项，2024年入选中国科学院理论物理研究所青年访问科学家项目。

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