科创中国

1量子几何相位理论及其应用简介

报告人：朱诗亮，南京大学物理学院

时间：12月27日（周四）16:00

单位：清华大学

地点：理科楼郑裕彤讲堂

相位因子被称为二十世纪理论物理学研究三大主旋律之一。几何相因子(几何相位)的提出是量子力学研究的开创性成果。相位因子是量子力学最核心的概念之一，对它的认识伴随着整个量子力学和量子场论的发展。薛定谔方程的提出，虚数i首次出现在物理学运动方程中，表明复数的引进不仅是数学工具的方便，更是量子力学描述世界的必须，相位开始成为物理学的核心概念。稍后，狄拉克引入波函数相位因子，并用它证明，如果世界上有一个磁单极，那么电荷必须是量子化的，这一优美的理论把相位和拓扑联系在一起。1954年，杨振宁-米尔斯非阿贝尔规范场理论的提出，把U(1)相位推广到SU(2)相位，构筑了粒子之间相互作用的基石。1959年，Aharonov 和Bohm 发现了AB相位，认识到要描述电磁场，场强不够，矢势更为基本。从1974年开始，杨振宁等用系列文章证明，要描述规范场，场强不足够，矢势有冗余，而相位因子恰好能描述规范势。

1984年，Berry发表了提出几何相位的论文。证明相因子只能分成动力学相位和几何相位。几何相位及其相关的Berry联络（Berry曲率）因深刻地反映了Hilbert空间的基本结构而在物理学的各个领域都有重要应用，这些领域包括较早的量子霍尔效应，及最近物理学的一些重要研究领域，如拓扑绝缘体和拓扑超导、量子计算、量子模拟等。在本报告中，我将主要介绍：(1) 相位和几何相位的简史；（2）几何相位在容错量子计算中的重要应用；（3）几何相位在超冷原子模拟人工规范势中的应用。量子计算和超冷原子量子模拟都是当代物理学研究的重要前沿课题。

2Observation of Higgs boson production in association with a topquarkpair (ttH) at the LHC with the ATLAS detector

报告人：Zhou Chen

时间：12月26日（周三）10:30

单位：清华大学

地点：物理系理科楼C302

Observation of Higgs boson production in association with a top quark pair (ttH) is presented, based on the analysis of up to 79.8 fb 1 of proton-proton collision data produced at 13 TeV center-of-mass energy by the Large Hadron Collider and recorded with the ATLAS detector. The results for Higgs boson decay channels of bb, diphoton, WW, ditau, and ZZ are combined. The observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the ttH searches using a dataset corresponding to integrated luminosities of 4.5 and 20.3 fb 1 at 7 and 8 TeV, respectively, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total ttH production cross section at 13 TeV is measured to be 670 ± 90 (stat.) +110/-100 (syst.) fb, while the Standard Model prediction is 507+35 50 fb. CERN issued a press release for both the ATLAS and CMS ttH results on June 4th 2018. Moreover, this talk will give detailed description of the new ttH (H→gamma gamma) analysis. Applying advanced machine learning package XGBoost BDT, exceptional performance is achieved by using object level kinematic variables from jets, leptons, and photons to separate the ttH signal from the background.

3Introduction to Gravitational Wave Activities at Hiroshima University

报告人：Helen Poon，Hiroshima University

单位：清华大学
时间：12月26日（周三）10:30

地点：蒙民伟科技南楼S727

Since LIGO detected GW150914, there has been a revolution in the field of astronomy. Japan has been making a lot of contribution to the understanding of gravitational waves. In the end of 2017, a nation-wide project called "Gravitational wave physics and astronomy: Genesis" has been set up which combines the effort of theories, observations and experiments. As an important collaboration institute, Hiroshima University contributes a lot in the field of high energy and optical observations. In this talk, I will introduce the gravitational wave activities in our group, including a CubeSat with good localization under development - CAMELOT, a UV-optical telescope in Tibet - Hinotori and the 1.5m optical-NIR telescope KANATA in East Hiroshima.

4ME-L穆勒矩阵椭偏仪在薄膜性能测试中的应用

报告人：郭春付

时间：12月26日（周三）13:30

单位：北京师范大学

地点：物理楼106

5Nanoplasmonics：from multi-dimensional information technologies to multi-functional metasurfaces

报告人：李向平，暨南大学

时间：12月26日（周三）15:10

单位：北京大学

地点：物理楼 中212

Surface plasmons (SPs) propagating along the interface between metals and dielectrics are capable of tailoring light matter interaction at the nanoscale, which emerges as a research frontier in nanophotonics. In this talk, we introduce the recent progress of multi-dimensional high capacity optical information storage and multi-functional metasurfaces by nanoplasmonics. As a consequence of resonant excitation of plasmonic nanoparticles, strong photothermal effect leads to permanent shape transitions, which unfolds a new platform for multiplexed information storage. Through the investigation of polarization-sensitive and orbital angular momentum sensitive plasmonic resonance in plasmonic nanostructures, information can be multiplexed in the multiple physical divisions of light for orders of magnitude increased information capacity. Moreover, metasurfaces composed of arrays of subwavelength artificial meta-atoms offer unprecedented capability of wavefront manipulation for a variety of applications. By structuring and patterning plasmonic nanostructures in a diatomic arrangement we demonstrate wide-angle and full-polarization controlled vectorial holography. Further, precise structuring the plasmonic nanostructures leads to vivid color generations. Color images can be encrypted in the angular anisotropy by utilizing the laser splashed 3D structures.

6高性能半导体太赫兹量子级联激光器及其应用

报告人：李联合，英国利兹大学

时间：12月27日（周四）10:30

单位：清华大学

地点：物理系理科楼B406

 半导体太赫兹(THz)量子级联激光器(QCL)是迄今为止唯一能够在THz波段实现连续工作的高功率、紧凑型固态相干辐射源。自2002年研制成功以来，就引起了人们的广泛关注和兴趣，并迅速成为THz研究领域的热点。经过不断的器件设计改进和性能提高，其工作频率已经可以覆盖1.2到5.6 THz，脉冲输出峰值功率达2.4 W。然而，由于基本物理机制的限制，目前THz QCL还需在低温200 K以下工作。尽管如此，采用斯特令制冷器的“turn-key” THz QCL系统却已出现在商用市场上。THz QCL的材料生长制备是一项极具挑战性的工作，仅有为数不多的研究所和大学有能力制备高性能器件。利兹大学是这一研究领域的先行者。经过十几年的不懈努力和探索，已经实现了器件的可控性生长，能够可重复性地制作实现各种频率的高性能THz QCL并成功将其应用在了商用THz系统中。这一报告将讨论这些高性能器件的生长制备、最新研究进展和部分应用。.

7A New X-Ray Selected Galaxy Cluster Sample from the ROSAT All-Sky Survey

报告人：Weiwei Xu，National Astronomical Observatories, Chinese Academy of Sciences

时间：12月27日（周四）12:00

单位：北京大学

地点：first floor meeting room, KIAA

Some indications for tension have long been identified between cosmological constraints obtained from galaxy clusters and primary cosmic microwave background (CMB) measurements. Typically, assuming the matter density and fluctuations, as parameterized with Omega_m and sigma_8, estimated from CMB measurements, many more clusters are expected than those actually observed. This has been reinforced recently by the Planck collaboration. One possible explanation could be that certain types of galaxy groups or clusters were missed in samples constructed in previous surveys, resulting in a higher incompleteness than estimated. In this work, we aim to determine if a hypothetical class of very extended, low-surface-brightness galaxy groups or clusters have been missed in previous X-ray cluster surveys based on the ROSAT All-Sky Survey (RASS).We applied a dedicated source-detection algorithm sensitive also to more unusual group or cluster surface-brightness distributions. We found many known groups but also a number of new group candidates, which are not included in any previous X-ray or SZ cluster catalogs. In this talk, I will present a pilot sample of 13 very extended groups discovered in the RASS at positions where no X-ray source has been detected previously and with clear optical counterparts. The X-ray fluxes of at least 5 of these are above the nominal flux-limits of previous RASS cluster catalogs (> 3x10^{-12} erg s^{-1} cm^{-2} in the 0.1-2.4 keV energy band). They have low mass (10^{13} Msun We demonstrate that galaxy groups were missed in previous RASS surveys, possibly due to the flat surface-brightness distributions of this potential new population. Analysis of the full sample will show if this might have a significant effect on previous cosmological parameter constraints based on RASS cluster surveys. 

8Star cluster formation at various scales: from galaxies to giant molecular clouds

报告人：Hui Li，MIT

时间：12月27日（周四）14:00

单位：清华大学

地点：蒙民伟科技南楼S727

Over the past decades, the discovery of a large number of young massive clusters (YMCs) in the local Universe and giant clumps in high-z galaxies suggests that clustered star formation is the dominant star formation mode. Mass and energy feedback from these enormous clusters is inevitably responsible for shaping the properties of their host galaxies. To model star formation in a more realistic way, I implemented a novel prescription in cosmological hydrodynamic simulations by treating star clusters as a unit of star formation. I tested this algorithm by running a suite of cosmological simulations with unprecedented parsec-scale spatial resolution. I found that various observed properties of host galaxies and star clusters are reproduced. Interestingly, we find some of these properties can be used to calibrate the subgrid models in the simulations. We follow the orbits of all simulated star clusters, estimate the cluster mass loss due to tidal disruption, and for the first time, investigate the connection between YMCs formed at high-z and the globular clusters observed at present. In parallel, to study how giant molecular clouds (GMCs) collapse to form star clusters and how they are eventually disrupted by stellar feedback from massive stars, I performed a suite of high-resolution hydrodynamic simulations of individual GMCs with self-consistent star formation and momentum feedback. I find that the final star cluster mass depends strongly on the surface density of the cloud due to the force balancing between gravity and momentum feedback.

9Proton-driven plasma wakefield acceleration (AWAKE), current status and future plans

报告人：Guoxing Xia，the University of Manchester and the Cockroft Institute

时间：12月28日（周五）09:30

单位：中科院高能物理所

地点：B326 main building

Proton-driven plasma wakefield acceleration (AWAKE), current status and future plans Plasma-based accelerators have achieved tremendous progress in the last three decades, thanks to the availability of ultrashort and high power lasers and relativistic electron beams. Nowadays, laser wakefield acceleration (LWFA) has routinely achieved GeV beam energy in centimeter long plasma channel. Electron beam driven plasma wakefield acceleration (PWFA) has achieved the energy doubling of a 42 GeV SLC electron beam at SLAC and proved the high efficiency acceleration for electrons and positrons, respectively. The new plasma-based acceleration experiment, so-called AWAKE at CERN has very recently demonstrated the successful acceleration of electrons to up to 2 GeV in a proton driven plasma wakefield. In this talk, I will introduce the basic principles and the development of proton-driven plasma wakefield acceleration scheme. The latest experimental results and its future plans.

10Star cluster formation at various scales: from galaxies to giant molecular clouds

报告人：Hui Li，MIT

时间：12月28日（周五）12:00

单位：北京大学

地点：KIAA, 1st meeting room

Over the past decades, the discovery of a large number of young massive clusters (YMCs) in the local Universe and giant clumps in high-z galaxies suggests that clustered star formation is the dominant star formation mode. Mass and energy feedback from these enormous clusters is inevitably responsible for shaping the properties of their host galaxies. To model star formation in a more realistic way, I implemented a novel prescription in cosmological hydrodynamic simulations by treating star clusters as a unit of star formation. I tested this algorithm by running a suite of cosmological simulations with unprecedented parsec-scale spatial resolution. I found that various observed properties of host galaxies and star clusters are reproduced. Interestingly, we find some of these properties can be used to calibrate the subgrid models in the simulations. We follow the orbits of all simulated star clusters, estimate the cluster mass loss due to tidal disruption, and for the first time, investigate the connection between YMCs formed at high-z and the globular clusters observed at present. In parallel, to study how giant molecular clouds (GMCs) collapse to form star clusters and how they are eventually disrupted by stellar feedback from massive stars, I performed a suite of high-resolution hydrodynamic simulations of individual GMCs with self-consistent star formation and momentum feedback. I find that the final star cluster mass depends strongly on the surface density of the cloud due to the force balancing between gravity and momentum feedback.  

11Non-equilibrium classification of topological phases: from free-fermion to correlated

报告人：刘雄军，Peking University

时间：12月28日（周五）15:00

单位：中科院物理研究所

地点：M楼236会议室

Topological phase of matter is a main stream of research in condensed matter physics. In this talk I introduce how to characterize topological phases by non-equilibrium quantum dynamics, and show its application to detecting topological physics with high precision. The framework of the theory consists of basic findings. First, we show that classifying a generic d-dimensional (dD) gapped topological phase with integer invariants can reduce to a (d-1)D invariant defined on so-called band inversion surfaces (BISs), rendering a bulk-surface duality. Further, we show in quenching across phase boundary the (pseudo)spin dynamics to exhibit emergent topological patterns on BISs, which are attributed to the post-quench bulk topology and manifest a dynamical bulk-surface correspondence. The topological phase is then classified by a dynamical topological invariant measured from the emergent dynamical field on the BISs. Applications to quenching experiments on feasible models are proposed and studied. The dynamical detection with high precision of the topological quantum physics has been achieved in experiments. We generalize this theory to correlated topological phase by quenching the spin-1/2 topological Haldane-Hubbard model. Novel correlation effects are shown in the non-equilibrium quantum dynamics for real spin and pseudospin spaces, with which both the topological phase and conventional magnetic order can be detected. These results may facilitate the experimental investigation of correlated topological physics.

12通往碳中和的高温熔盐电化学新技术

报告人：汪的华，武汉大学

时间：12月29日（周六）10:00

单位：中科院高能物理所

地点：C305会议室

本报告在介绍 CO2 电化学和熔盐CO2捕集与电化学转化(MSCC-ET)技术的基础上，主要报告本课题组在熔盐CO2捕集吸收、电化学还原的过程机理、还原产物的表征和应用、电解体系关键材料以及技术放大方面的若干研究进展。

更多报告信息：中国物理学会期刊网学术讲座列表

1. 一幅图读懂量子力学（下）

2. 真空不空| 涂涛 郭光灿

3. 吾爱吾师及真理——大师间的师生情 | 周末大家谈

4. 为纪念物理大师费曼百年诞辰而作 | 赵凯华

5. 纪念费曼 | 姬扬

6. 关于统计力学的基本原理 | 郑伟谋

7. 物理英才‖曹则贤带你解析大自然的花样

8. 超导“小时代”之三十七：超导之从鱼到渔

9. 科学的一生——怀念父亲程开甲 | 程漱玉

10. 量子十问之二：“爱因斯坦幽灵”能用来实现超光速通信吗？| 郭光灿

END