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報告人：Jacob Khurgin，約翰霍普金斯大學

時間：3月4日（周二）10:00

單位：北京大學物理學院

地點：物理學院思源多功能廳（西301）

摘要：

長期以來，光學器件和系統的功能性一直受到材料的折射率范圍極為有限的制約。尤其在當前光學領域最為活躍的研究方向——集成光子學、光子晶體、超材料和超表面中，這一限制顯得尤為突出。僅僅將折射率提高50%，就可能帶來不成比例的性能提升。基于這一背景，報告人將探討折射率隨波長變化的基本限制因素，分析為何高折射率材料至今尚未問世，并指出一些可能的方向。在報告的第二部分，討論與此密切相關的問題：如何通過調節折射率實現高效的光學調制。總體來看，除非出現革命性的材料系統，否則現有調制技術的性能提升將是漸進式的，而非根本性的，且短期內難以實現數量級的突破。報告人將闡述如何通過集體效應和快速相變來實現未來的重大突破。

報告人簡介：

Jacob Khurgin是約翰霍普金斯大學電子與計算機工程系教授，美國物理學會會士（APS Fellow）、美國光學學會會士（Optica Fellow），以其在光學、電子學、凝聚態物理和通信領域的廣泛研究而著稱。他出版了《慢光——科學與應用》一書，全面介紹了慢光基本原理、潛在應用和發展前沿；參與編寫了八部著作，擁有40項專利，并在同行評審期刊上發表了340篇論文。其研究成果催生了眾多創新，從日常小家電（如電動剃須刀和咖啡機）到復雜的激光通信和化學檢測系統等多種應用。他是美國物理學會量子電子學聯合委員會的成員，曾擔任超過60場學術會議的技術程序委員會成員。此外，他還曾在普林斯頓大學、加州大學洛杉磯分校、布朗大學、蘇黎世聯邦理工學院和巴黎高等師范學校等多個知名學府擔任訪問教授。

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報告人：David Stephen，Quantinuum

時間：3月5日（周三）10：00

單位：中國科學院理論物理物理所

騰訊會議: 326-619-535

密碼: 2636

摘要：

In this talk,?I will begin by describing a new universal scheme of measurement-based quantum computation. This scheme has some practical advantages,?but it comes at the cost of having an unusual gate set consisting of rotations generated by long Pauli strings. I will then pivot into discussing such gate sets,?including how to identify when they are universal and how to compile quantum algorithms with them. I will also show how certain universal gate sets generate all unitaries faster than others,?explain this in terms of the fraction of anticommuting pairs of generators,?and discuss potential implications to fault-tolerant quantum computation. Overall,?these results reveal the necessity and intrigue of considering universal gate sets with distinct structure and properties compared to standard gate sets.

報告人簡介：

Dr. Stephen obtained a Master's degree at the University of British Columbia with R. Raussendorf,?and a PhD at the Max Planck Institute of Quantum Optics with N. Schuch. After doing a Postdoc at the University of Colorado Boulder and Caltech,?he moved to Quantinuum where he now works on quantum algorithms. In the past,?his research has looked at alternative types of quantum computation such as measurement-based quantum computation,?and related them to the physics of quantum many-body systems. He is currently interested in problems related to efficient quantum state preparation and quantum circuit compilation.

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報告人：劉文淵，浙江大學

時間：3月5日（周三）15:00

單位：北京大學物理學院

地點：北京大學物理樓，西563會議室

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報告人：Prof. Jacob Khurgin，約翰霍普金斯大學

時間：3月6日（周四）15:00

單位：北京大學物理學院

地點：物理樓西202報告廳

摘要：

Recent interest in non-Hermitian quantum mechanics stems from the discovery of exceptional points (EPs), which mark the transition between regions of preserved and broken parity-time (PT) symmetry, where Hamiltonian eigenfunctions become degenerate. In photonics, PT symmetry arises from non-Hermiticity, represented by gain and loss. In the first part of this talk I show that eigenmodes of active, pumped cavity polaritons with population inversion exhibit features resembling PT symmetry. In the second part of the talk, I consider in depth the possibility of realizing asymmetric mode switching and omni-polarizer action through the dynamic encirclement of Eps and offer a new perspective on the operating principle of these devices. The experimentally confirmed proposed concept of “encirclement emulators” may allow a better assessment of the limitations, practical potential, and applications of EP encirclements in non-Hermitian photonics.

報告人簡介：

Jacob Khurgin, a professor of electrical and computer engineering at Johns Hopkins University, is known for his diverse and eclectic research in the areas of optics, electronics, condensed matter physics, and telecommunications. He has published eight book chapters, 40 patents, 340 papers in refereed journals. The insights that have emerged from his research have led to numerous inventions ranging from small appliances, such as electric shavers and coffeemakers, to sophisticated systems for laser communication and chemical detection. He is a member of the American Physical Society Joint Council on Quantum Electronics and has served as a technical program committee member for more than 60 academic conferences. He has held visiting professorships at numerous institutions, including Princeton, UCLA, Brown, ETH in Zurich, and Ecole Normale Superieure in Paris. He was named a Fellow by the American Physical Society and the Optical Society of America.

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報告人：張童，復旦大學

時間：3月6日（周四）16：00

單位：北京大學物理學院

地點：物理樓（附中南側）W101

摘要：

In type-II superconductors, external magnetic field induces the formation of quantized flux/vortex. These vortices carry information of superconducting pairing and can host exotic quasiparticles, such as Caroli-de Gennes-Matricon (CdGM) states and Majorana zero modes (MZMs). Additionally, the response of vortices to external electrical current, such as vortex pinning effect, profoundly influences the transport properties of practical superconductors. In this talk, I will present our microscopic studies of vortex state in iron-based superconductors, including (Li,Fe)OHFeSe and 1ML FeSe/STO. Utilizing high-energy resolution scanning tunneling spectroscopy, we observed zero-energy modes, CdGM states and determined their spatial distributions. The zero-mode show characteristics of MZM. Furthermore, we explored vortex pinning effects at atomic-scale. We found that defect-vortex interactions shift low-energy CdGM states away from Fermi energy, thereby reducing the vortex energy and explained why the vortices are pinned by point defects. Based on these findings, we propose a general mechanism of vortex pinning in superconductors.

報告人簡介：

張童，2004 年本科畢業于山東大學物理系， 2010 年于中國科學院物理研究所獲得博士學位， 2010-2012 年在美國 NIST 做博士后研究，現任復旦大學物理系教授。主要利用極低溫掃描隧道顯微鏡 (STM) 、高分辨隧道譜、外延薄膜生長等研究非常規超導體和拓撲材料。在包括 Nat. Phys. ， PRL ， PRX ， Sci. Adv. ， Nat. Communi. 在內的期刊上發表論文 60 余篇，被引 6 千余次。

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報告人：趙宏政，北京大學

時間：3月7日（周五）10:00

單位：南方科技大學物理系

鏈接：

摘要：

We present a general driving protocol for many-body systems to generate a sequence of prethermal regimes, each exhibiting a lower symmetry than the preceding one. We provide an explicit construction of effective Hamiltonians exhibiting these symmetries. This imprints emergent quasi-conservation laws hierarchically, enabling us to engineer the respective symmetries and concomitant orders in nonequilibrium matter. We provide explicit examples, including spatiotemporal and topological phenomena, as well as a spin chain realizing the symmetry ladder SU(2)→U(1)→Z2→E. Based on this framework, we further construct a protocol that leads to emergent massive Nambu–Goldstone quasi-particles with tunable spectral mass gap and lifetime.

報告人簡介：

趙宏政，北京大學物理學院凝聚態所助理教授。2017年于山東大學泰山學堂本科畢業，2021年倫敦帝國理工博士畢業，隨后兩年在德國馬克斯-普朗克復雜系統物理研究所從事博士后研究工作，后于2023年加入北大物理學院。長期從事非平衡多體動力學理論研究，研究興趣包括量子熱化，驅動系統，強關聯系統，量子模擬與量子計算。

封面圖片來源：https://www.x-mol.com/paper/1819458854445973504/t?adv

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