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Uniquely identifying topological order based on boundary-bulk duality and anyon condensation

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National science Review 2023年第3期10卷 117-126页

作者： Yong-Ju Hai Ze Zhang Hao Zheng Liang Kong Jiansheng Wu Dapeng Yu shenzhen institute for quantum science and engineering Southern University of Science and Technology department of physics Southern University of Science and Technology International quantum Academy Guangdong Provincial Key Laboratory of quantum science and engineering

Topological order is a new quantum phase that is beyond Landau’ s symmetry-bre aking paradigm.Its defining features include robust degenerate ground states,long-range entanglement and anyons.It was known that R and F matrices,which characterize the fusion-braiding properties of anyons,can be used to uniquely identify topological order.In this article,we explore an essential question:how can the R and F matrices be experimentally measured?We show that the braidings,i.***.the R matrices,can be completely determined by the half braidings of boundary excitations due to the boundary-bulk duality and the anyon condensation.The F matrices can also be measured by comparing the quantum states involving the fusion of three anyons in two different orders.Thus we provide a model-independent experimental protocol to uniquely identify topological order.By using quantum simulations based on a toric code model with boundaries encoded in three-and four-qubit systems and state-of-the-art technology,we obtain the first experimental measurement of R and F matrices by means of an NMR quantum computer at room temperature.

关键词： topological order R matrix F matrix bulk-boundary duality anyon condensation

3D quantum Hall effect

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National science Review 2019年第2期6卷 208-210页

作者： Hai-Zhou Lu Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology (SUSTech) shenzhen Key Laboratory of quantum science and engineering

The discovery of the quantum Hall effect in 2D systems opens the door to topological phases of matter. A quantum Hall effect in three dimensions is a long-sought phase of matter and has inspired many efforts and claim... 详细信息

关键词： In quantum Hall effect

Intrinsic magnetic topological materials

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Frontiers of physics 2023年第2期18卷 131-160页

作者： Yuan Wang Fayuan Zhang Meng Zeng Hongyi Sun Zhanyang Hao Yongqing Cai Hongtao Rong Chengcheng Zhang Cai Liu Xiaoming Ma Le Wang Shu Guo Junhao Lin Qihang Liu Chang Liu Chaoyu Chen shenzhen institute for quantum science and engineering(SIQSE)and department of physics Southern University of Science and Technology(SUSTech)Shenzhen 518055China

Topological states of matter possess bulk electronic structures categorized by topological invariants and edge/surface states due to the bulk-boundary correspondence. Topological materials hold great potential in the development of dissipationless spintronics, information storage and quantum computation, particularly if combined with magnetic order intrinsically or extrinsically. Here, we review the recent progress in the exploration of intrinsic magnetic topological materials, including but not limited to magnetic topological insulators, magnetic topological metals, and magnetic Weyl semimetals. We pay special attention to their characteristic band features such as the gap of topological surface state, gapped Dirac cone induced by magnetization (either bulk or surface), Weyl nodal point/line and Fermi arc, as well as the exotic transport responses resulting from such band features. We conclude with a brief envision for experimental explorations of new physics or effects by incorporating other orders in intrinsic magnetic topological materials.

关键词： intrinsic magnetic topological insulator magnetic topological metals magnetic Weyl semimetal topological surface states magnetic gap

Dual-compressed photoacoustic single-pixel imaging

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National science Review 2023年第1期10卷 187-195页

作者： Yuning Guo Baowen Li Xiaobo Yin department of Mechanical engineering University of Colorado department of Material science and engineering Department of Physics Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Materials science and engineering Program University of Colorado

Photoacoustic imaging,an acoustic imaging modality with potentially optical resolution in an optical turbid medium,has attracted great attention.However,the convergence of wavefront optimization and raster scanning in computational photoacoustic imaging leads to the challenge of fast mapping,especially for a spatial resolution approaching the acoustic deep-subwavelength regime.As a sparse sampling paradigm,compressive sensing has been applied in numerous fields to accelerate data acquisition without significant quality losses.In this work,we propose a dual-compressed approach for photoacoustic surface tomography that enables high-efficiency imaging with 3D spatial resolution unlimited by the acoustics in a turbid environment.The dual-compressed photoacoustic imaging with single-pixel detection,enabled by spatially optical modulation with synchronized temporally photoacoustic coding,allows decoding of the fine optical information from the modulated acoustic signal even when the variance of original photoacoustic signals is weak.We perform a proof-of-principle numerical demonstration of dual-compressed photoacoustic imaging, that resolves acoustic sub-acoustic-wavelength details with a significantly reduced number of measurements,revealing the potential for dynamic imaging.The dual-compressed concept,which transforms unobtrusive spatial difference into spatio-temporal detectable information,can be generalized to other imaging modalities to re alize efficient,high-spatial-resolution imaging.

关键词： photoacoustic imaging compressive sensing single-pixel imaging surface tomography

quantum supremacy: some fundamental concepts

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National science Review 2019年第1期6卷 22-23页

作者： Man-Hong Yung Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology shenzhen Key Laboratory of quantum science and engineering Southern University of Science and Technology

quantum computation was envisioned by Feynman as a valuable means of solving quantum problems [1]. The question is, how do we prove the superiority of quantum computing over classical devices? A common misconception in describing the power of a quantum computer over a classical computer is that quantum bits can be prepared in a superposition of an exponential number of states, which cannot be achieved with classical bits. This statement is certainly true, but it does not tell us, specifically,what problems quantum computers can

关键词： quantum supremacy some fundamental concepts

Evidence for topological superconductivity: Topological edge states in Bi2Te3/FeTe heterostructure

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Chinese physics B 2020年第9期29卷 45-50页

作者：郭斌师凯歌秦海浪周良陈伟强叶飞梅佳伟何洪涛潘天洛王干 shenzhen institute for quantum science and engineering&department of physics Southern University of Science and TechnologyShenzhen 518055China Guangdong Provincial Key Laboratory of quantum science and engineering Shenzhen Institute for Quantum Science and EngineeringSouthern University of Science and TechnologyShenzhen 518055China

Majorana fermions have been predicted to exist at the edge states of a two-dimensional topological superconductor.We fabricated single quintuple layer(QL)Bi2Te3/FeTe heterostructure with the step-flow epitaxy method and studied the topological properties of this system by using angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy.We observed the coexistence of robust superconductivity and edge states on the single QL Bi2Te3 islands which can be potential evidence for topological superconductor.

关键词： Bi2Te3/FeTe heterostructure topological superconductivity edge states scanning tunnelling microcopy

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Robust twin-field quantum key distribution through sending or not sending

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National science Review 2023年第4期10卷 76-85页

作者： Cong Jiang Zong-Wen Yu Xiao-Long Hu Xiang-Bin Wang Jinan institute of quantum Technology State Key Laboratory of Low Dimensional quantum physics Department of Physics Tsinghua University Data Communication science and Technology Research institute School of physics State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen University Shanghai Branch CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China shenzhen institute for quantum science and engineering and Physics Department Southern University of Science and Technology Frontier science Center for quantum Information

The sending-or-not-sending(SNS) protocol is one of the most major variants of the twin-field(TF)quantum key distribution(QKD) protocol and has been realized in a 511-km field fiber, the farthest field experiment to date. In practice, however, all decoy-state methods have unavoidable source errors, and the source errors may be non-random, which compromises the security condition of the existing TF-QKD protocols. In this study, we present a general approach for efficiently calculating the SNS protocol’s secure key rate with source errors, by establishing the equivalent protocols through virtual atenuation and the tagged model. This makes the first result for TF QKD in practice where source intensity cannot be controlled exactly. Our method can be combined with the two-way classical communication method such as active odd-parity pairing to further improve the key rate. The numerical results show that if the intensity error is within a few percent, the key rate and secure distance only decrease marginally. The key rate of the recent SNS experiment in the 511-km field fiber is still positive using our method presented here, even if there is a ±9.5% intensity fluctuation. This shows that the SNS protocol is robust against source errors.

关键词： quantum information quantum key distribution sending or not sending twin field source error

On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family

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National science Review 2024年第2期11卷 50-64页

作者： Yuan Wang Xiao-Ming Ma Zhanyang Hao Yongqing Cai Hongtao Rong Fayuan Zhang Weizhao Chen Chengcheng Zhang Junhao Lin Yue Zhao Chang Liu Qihang Liu Chaoyu Chen shenzhen institute for quantum science and engineering(SIQSE)and department of physics Southern University of science and Technology(SUSTech)

We review recent progress in the electronic structure study of intrinsic magnetic topological insulators(MnBi2Te4)·(Bi2Te3)n(n = 0, 1, 2, 3) family. Specifically, we focus on the ubiquitously(nearly)gapless behavior of the topological Dirac surface state observed by photoemission spectroscopy, even though a large Dirac gap is expected because of surface ferromagnetic order. The dichotomy between experiment and theory concerning this gap behavior is perhaps the most critical and puzzling question in this frontier. We discuss various proposals accounting for the lack of magnetic effect on the topological Dirac surface state, which are mainly categorized into two pictures, magnetic reconfiguration and topological surface state redistribution. Band engineering towards opening a magnetic gap of topological surface states provides great opportunities to realize quantized topological transport and axion electrodynamics at higher temperatures.

关键词： intrinsic magnetic topological insulator topological surface states magnetic gap magnetic reconfiguration topological surface state redistribution van der Waals spacing expansion

Cooper instability and superconductivity of the Penrose lattice

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science China(physics,Mechanics & Astronomy) 2022年第8期65卷 110-120页

作者： Yu-Bo Liu Juan-Juan Hao Yongyou Zhang Ye Cao Wei-Qiang Chen Fan Yang School of physics Beijing Institute of TechnologyBeijing100081China department of physics Southern University of Science and TechnologyShenzhen518055China shenzhen institute for quantum science and engineering Southern University of Science and TechnologyShenzhen518055China shenzhen Key Laboratory of Advanced quantum Functional Materials and Devices Southern University of Science and TechnologyShenzhen518055China

Bulk superconductivity(SC) has recently been observed in the Al-Zn-Mg quasicrystal(QC). To settle several fundamental issues of the SC on the QC, we use an attractive Hubbard model to perform a systematic study on the Penrose lattice. The first issue is the Cooper instability of the QC, i.e., no Fermi surface under an infinitesimal attractive interaction. Starting from the two-electron problem outside a filled Fermi sea, we analytically prove that an infinitesimal Hubbard attraction can lead to the Cooper instability as long as the density of the state is nonzero at the Fermi level. The findings provide a basis for the SC on the QC. Our numerical results show that the Cooper pairing always takes place between two time-reversal states, satisfying Anderson’s theorem. On this theorem, we perform a mean-field(MF) study at zero and finite temperatures. The MF study shows that an arbitrarily weak attraction can lead to a pairing order, with the resulting pairing state being well described by the Bardeen-Cooper-Schrieffer theory and the thermal dynamic behaviors being well consistent with the experimental results. The second issue is about the superfluid density on the QC without translational symmetry. Our findings clarify that although the normal state of the system locates at the critical point of the metal-insulator transition, the pairing state exhibits a real SC, carrying finite superfluid density that can be verified by the Meissner effect. This finding is consistent with the experiment results. This study also reveals that the properties of the SC on the Penrose lattice are universal for all QCs.

关键词： superconductivity quasicrystal cooper instability

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