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Security of quantum key distribution with virtual mutually unbiased bases

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science China(physics,Mechanics & Astronomy) 2024年第7期67卷 13-21页

作者： hong-Wei Li Chen-Peng Hao Zhi-Jiang Chen Li Gong Yi-Fei Lu Yang Wang Jia-Ji Li Chun-Mei Zhang Rong Wang Zhen-Qiang Yin Qing-Yu Cai Henan Key Laboratory of quantum information and Cryptography SSF IEUZhengzhou 450000China institute of quantum information and technology Nanjing University of Posts and TelecommunicationsNanjing 210003China department of physics University of Hong KongHong Kong 999077China Key Laboratory of quantum information University of Science and Technology of ChinaHefei 230026China School of information and Communication Engineering Hainan UniversityHaikou 570228China

In a perfect quantum key distribution(QKD)protocol,quantum states should be prepared and measured with mutually unbiased bases(MUBs).However,in a practical QKD system,quantum states are generally prepared and measured with imperfect MUBs using imperfect devices,possibly reducing the secret key rate and transmission *** analyze the security of a QKD system with imperfect MUBs,we propose virtual MUBs to characterize the quantum channel against collective attack,and analyze the corresponding secret key rate under imperfect state preparation and measurement *** generally,we apply the advantage distillation method for analyzing the security of QKD with imperfect MUBs,where the error tolerance and transmission distance can be sharply *** analysis method can be applied to benchmark and standardize a practical QKD system,elucidating the security analysis of different QKD protocols with imperfect devices.

关键词： quantum key distribution mutually unbiased bases advantage distillation

Progress on the antiferromagnetic topological insulator MnBi2Te4

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National science Review 2024年第2期11卷 33-49页

作者： Shuai Li Tianyu Liu Chang Liu Yayu Wang Hai-Zhou Lu X.C.Xie department of physics Harbin Institute of Technology Shenzhen institute for quantum science and Engineering and department of physics Southern University of Science and Technology(SUSTech) quantum science Center of Guangdong-hong kong-Macao Greater Bay Area(Guangdong) Shenzhen Key Laboratory of quantum science and Engineering International quantum Academy Beijing Academy of quantum information sciences Beijing Key Laboratory of Optoelectronic Functional Materials&Micro-Nano Devices Department of Physics Renmin University of China State Key Laboratory of Low Dimensional quantum physics Department of PhysicsTsinghua University Frontier science Center for quantum information Hefei National Laboratory International Center for quantum Materials School of Physics Peking University institute for Nanoelectronic Devices and quantum Computing Fudan University

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed maTher physics. They represent a new class of materials exhibiting nontrivial topological phases,and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous Hall effect and the quantum spin Hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic *** particular, the quantum anomalous Hall and axion insulator phases can be realized in topological insulators with magnetic order. MnBi2Te4, as the first intrinsic antiferromagnetic topological insulator discovered, allows the examination of existing theoretical predictions; it has been extensively studied, and many new discoveries have been made. Here we review the progress made on MnBi2Te4from both experimental and theoretical aspects. The bulk crystal and magnetic structures are surveyed first, followed by a review of theoretical calculations and experimental probes on the band structure and surface states, and a discussion of various exotic phases that can be realized in MnBi2Te4. The properties of MnBi2Te4thin films and the corresponding transport studies are then reviewed, with an emphasis on the edge state transport. Possible future research directions in this field are also discussed.

关键词： MnBi2Te4 magnetic topological insulator antiferromagnetic quantum anomalous Hall effect axion insulator

Excitonic Instability in Ta2Pd3Te5 Monolayer

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Chinese physics Letters 2024年第9期41卷 57-62页

作者： Jingyu Yao Haohao Sheng Ruihan Zhang Rongtian Pang Jin-Jian Zhou Quansheng Wu hongming Weng Xi Dai Zhong Fang Zhijun Wang Beijing National Laboratory for Condensed Matter physics and Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of sciences Beijing 100049China Centre for quantum physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing 100081China department of physics Hong Kong University of Science and TechnologyHong Kong 999077China

By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)*** bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained through exfoliation or molecular-beam ***-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson *** to the same symmetry of the band-edge states,the two-dimensional polarization 2D would be finite as the band gap goes to zero,allowing for an EI state in the *** the first-principles many-body perturbation theory,the GW plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap,indicating the excitonic *** computed phonon spectrum suggests that the monolayer is dynamically stable without lattice *** findings suggest that the Ta_(2)Pd_(3)Te_(5) monolayer is an excitonic insulator without structural distortion.

关键词： monolayer principles calculations

Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown Mn Bi2Te4 thin films

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National science Review 2024年第2期11卷 24-32页

作者： Yunhe Bai Yuanzhao Li Jianli Luan Ruixuan Liu Wenyu Song Yang Chen Peng-Fei Ji Qinghua Zhang Fanqi Meng Bingbing Tong Lin Li Yuying Jiang Zongwei Gao Lin Gu Jinsong Zhang Yayu Wang Qi-Kun Xue Ke He Yang Feng Xiao Feng State Key Laboratory of Low Dimensional quantum physics Department of Physics Tsinghua University institute of physics Chinese Academy of Sciences School of Materials science and Engineering Tsinghua University Beijing Academy of quantum information sciences Frontier science Center for quantum information Hefei National Laboratory Southern University of science and technology

The intrinsic magnetic topological insulator MnBi2Te4provides a feasible pathway to the high-temperature quantum anomalous Hall（QAH） effect as well as various novel topological quantum phases. Although quantized transport properties have been observed in exfoliated MnBi2Te4thin flakes, it remains a big challenge to achieve molecular beam epitaxy（MBE）-grown MnBi2Te4thin films even close to the quantized regime. In this work, we report the realization of quantized anomalous Hall resistivity in MBE-grown MnBi2Te4thin films with the chemical potential tuned by both controlled in situ oxygen exposure and top gating. We find that elongated post-annealing obviously elevates the temperature to achieve quantization of the Hall resistivity, but also increases the residual longitudinal resistivity, indicating a picture of high-quality QAH puddles weakly coupled by tunnel barriers. These results help to clarify the puzzles in previous experimental studies on MnBi2Te4and to find a way out of the big difficulty in obtaining MnBi2Te4samples showing quantized transport properties.

关键词： intrinsic magnetic topological insulator quantized anomalous Hall resistivity molecular beam epitaxy quantized transport property

Emergent symmetry in quantum phase transition:From deconfined quantum critical point to gapless quantum spin liquid

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science Bulletin 2024年第2期69卷 190-196页

作者： Wen-Yuan Liu Shou-Shu Gong Wei-Qiang Chen Zheng-Cheng Gu department of physics The Chinese University of Hong KongHong KongChina Division of Chemistry and Chemical Engineering California Institute of TechnologyPasadena CA 91125USA School of Physical sciences Great Bay UniversityDongguan 523000China Great Bay institute for Advanced Study Dongguan 523000China department of physics and Shenzhen institute for quantum science and Engineering Southern University of Science and TechnologyShenzhen 518055China Shenzhen Key Laboratory of Advanced quantum Functional Materials and Devices Southern University of Science and TechnologyShenzhen 518055China

The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase *** we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena,i.e.,the deconfined quantum critical point(DQCP)and the quantum spin liquid(QSL)*** large-scale tensor network simulations,we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic(AFM)model,namely the J1x-J1y-J2 model,which contains anisotropic nearestneighbor couplings J1x,J1y and the next nearest neighbor coupling *** small J1y/J1x,by tuning J2,a direct continuous transition between the AFM and valence bond solid phase is *** growing J1y/J1x,a gapless QSL phase gradually emerges between the AFM and VBS *** observe an emergent O(4)symmetry along the AFM–VBS transition line,which is consistent with the prediction of DQCP *** surprisingly,we find that such an emergent O(4)symmetry holds for the whole QSL–VBS transition line as *** findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view,and strongly constrain the quantum field theory description of the QSL *** phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.

关键词： Tensor network quantum phase transition Emergent symmetry quantum spin liquid Deconfined quantum critical point Anisotropic

Atom-referenced and stabilized soliton microcomb

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science China(physics,Mechanics & Astronomy) 2024年第2期67卷 2-8页

作者： Rui Niu Shuai Wan Tian-Peng Hua Wei-Qiang Wang Zheng-Yu Wang Jin Li Zhu-Bo Wang Ming Li Zhen Shen Yu Robert Sun Shui-Ming Hu Brent ELittle Sai Tak Chu Wei Zhao Guang-Can Guo Chang-Ling Zou Yun-Feng Xiao Wen-Fu Zhang Chun-Hua Dong State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi’an 710119China CAS Key Laboratory of quantum information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum information and quantum physics University of Science and Technology of ChinaHefei 230026China University of Chinese Academy of sciences Beijing 100049China department of Chemical physics University of Science and Technology of ChinaHefei 230026China department of physics and Materials science City University of Hong KongHong Kong 999077China State Key Laboratory for Mesoscopic physics and Frontiers science Center for Nano-optoelectronics School of PhysicsPeking UniversityBeijing 100871China

For the applications of the frequency comb in microresonators,it is essential to obtain a fully frequency-stabilized microcomb laser *** this study,we present a system for generating a fully atom-referenced stabilized soliton *** pump light around 1560.48 nm is locked to an ultra-low-expansion(ULE)*** pump light is then frequency-doubled and referenced to the atomic transition *** repetition rate of the soliton microcomb is injection-locked to an atomic-clockstabilized radio frequency(RF)source,leading to mHz stabilization at 1 *** a result,all comb lines have been frequencystabilized based on the atomic reference and the ULE cavity,achieving a very high precision of approximately 18 Hz at 1 s,corresponding to the frequency stability of 9.5×10^(-14).Our approach provides a fully stabilized microcomb experiment scheme with no requirement of f-2f technique,which could be easily implemented and generalized to various photonic platforms,thus paving the way towards the ultraprecise optical sources for high precision spectroscopy.

关键词： microcavity frequency comb dissipative Kerr solitons fully stabilized microcomb

quantum control for time-dependent noise by inverse geometric optimization

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science China(physics,Mechanics & Astronomy) 2024年第9期67卷 51-57页

作者： Xiaodong Yang Yingcheng Li Ran Liu Xinfang Nie Tao Xin Dawei Lu Jun Li institute of quantum Precision Measurement State Key Laboratory of Radio Frequency Heterogeneous IntegrationCollege of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China State Key Laboratory of Surface physics Department of PhysicsCenter for Field Theory and Particle Physicsand Institute for Nanoelectronic Devices and Quantum ComputingFudan UniversityShanghai 200433China Shenzhen institute for quantum science and Engineering and department of physics Southern University of Science and TechnologyShenzhen 518055China Guangdong Provincial Key Laboratory of quantum science and Engineering Southern University of Science and TechnologyShenzhen 518055China quantum science Center of Guangdong-hong kong-Macao Greater Bay Area(Guangdong) Shenzhen 518045China

quantum systems are exceedingly difficult to engineer because they are sensitive to various types of *** particular,timedependent noises are frequently encountered in experiments but how to overcome them remains a challenging *** this work,we propose a flexible robust control technique to resist time-dependent noises based on inverse geometric optimization working in the filter-function *** basic idea is to parameterize the control filter function geometrically and minimize its overlap with the noise spectral *** then effectively reduces the noise susceptibility of the controlled system *** show that the proposed method can produce high-quality robust pulses for realizing desired quantum evolutions under realistic noise ***,we demonstrate this method in examples including dynamical decoupling and quantum sensing protocols to enhance their performances.

关键词： time-dependent noise robust control quantum gates and states dynamical decoupling quantum sensing

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Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators

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National science Review 2024年第2期11卷 15-23页

作者： Rui Chen Hai-Peng Sun Mingqiang Gu Chun-Bo Hua Qihang Liu Hai-Zhou Lu X.C.Xie Shenzhen institute for quantum science and Engineering and department of physics Southern University of Science and Technology(SUSTech) International quantum Academy institute for Theoretical physics and Astrophysics University of Würzburg School of Electronic and information Engineering Hubei University of Science and Technology Guangdong Provincial Key Laboratory of Computational science and Material Design Southern University of Science and Technology Shenzhen Key Laboratory of quantum science and Engineering International Center for quantum Materials School of PhysicsPeking University Collaborative Innovation Center of quantum Matter CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences

The layer Hall effect describes electrons spontaneously deflected to opposite sides at different layers, which has been experimentally reported in the MnBi2Te4thin films under perpendicular electric fields. Here, we reveal a universal origin of the layer Hall effect in terms of the so-called hidden Berry curvature, as well as material design principles. Hence, it gives rise to zero Berry curvature in momentum space but non-zero layer-locked hidden Berry curvature in real space. We show that, compared to that of a trivial insulator, the layer Hall effect is significantly enhanced in antiferromagnetic topological insulators. Our universal picture provides a paradigm for revealing the hidden physics as a result of the interplay between the global and local symmetries, and can be generalized in various scenarios.

关键词： layerHall effect hidden Berry curvature antiferromagnetic insulator axion insulator, quantum transport

Entangled photons enabled ultrafast stimulated Raman spectroscopy for molecular dynamics

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Light(science & Applications) 2024年第8期13卷 1615-1622页

作者： Jiahao Joel Fan Zhe-Yu Ou Zhedong Zhang department of physics City University of Hong KongKowloonHong Kong SARChina City University of hong kong Shenzhen Research InstituteShenzhenGuangdongChina

quantum entanglement has emerged as a great resource for studying the interactions between molecules and *** propose a new scheme of stimulated Raman scattering with entangled photons.A quantum ultrafast Raman spectroscopy is developed for condensed-phase molecules,to monitor the exciton populations and *** results are obtained,showing an entanglement-enabled time-frequency scale not attainable by classical *** Raman signal presents an unprecedented selectivity of molecular correlation functions,as a result of the hong-Ou-Mandel *** work suggests a new paradigm of using an unconventional interferometer as part of spectroscopy,with the potential to unveil advanced information about complex materials.

关键词： materials. spectroscopy selectivity