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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

All-electrical switching of a topological non-collinear antiferromagnet at room temperature

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National Science Review 2023年第2期10卷 123-130页

作者： Yongcheng Deng Xionghua Liu Yiyuan Chen Zongzheng Du Nai Jiang Chao Shen Enze Zhang Houzhi Zheng Hai-Zhou Lu Kaiyou Wang State Key Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Institute for quantum Science and Engineering and Department of Physics Southern University of Science and Technology (SUSTech) International Quantum Academy Beijing academy of quantum Information Sciences Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences

Non-collinear antiferromagnetic Weyl semimetals,combining the advantages of a zero stray field and ultrafast spin dynamics,as well as a large anomalous Hall effect and the chiral anomaly of Weyl fermions,have attracted extensive interest.However,the all-electrical control of such systems at room temperature,a crucial step toward practical application,has not been reported.Here,using a small writing current density of around 5 × 106A·cm-2,we realize the all-electrical current-induced deterministic switching of the non-collinear antiferromagnet Mn3Sn,with a strong readout signal at room temperature in the Si/SiO2/Mn3Sn/AlOxstructure,and without external magnetic field or injected spin current.Our simulations reveal that the switching originates from the current-induced intrinsic non-collinear spin-orbit torques in Mn3Sn itself.Our findings pave the way for the development of topological antiferromagnetic spintronics.

关键词： spintronics non-collinear antiferromagnetic Weyl semimetals all-electrical switching spin-orbit torques

Superconductivity in topological semimetals

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National Science Review 2019年第2期6卷 199-202页

作者： Jian Wang international Center for quantum Materials School of Physics Peking University Collaborative Innovation Center of quantum Matter CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences Beijing academy of quantum Information Sciences

Topological superconductors, where the bulk state shows superconducting gap and Majorana fermions constitute gapless edge states, have become one of the most important topics in physical sciences. Majorana fermions are their own antiparticles and Majorana quasiparticles in a solid-state system obey non-Abelian statistics, and thus can be used for faulttolerant topological quantum computation.

关键词： As Superconductivity in topological semimetals

InAs/(In)GaSb-superconductor heterostructures:Materials and devices

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Science China(Physics,Mechanics & Astronomy) 2023年第6期66卷 74-85页

作者： Rui-Rui Du international Center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of SciencesBeijing 100190China

This article will briefly describe a Majorana platform made of InAs/GaSb(including InAs/(In)GaSb)semiconductor-superconductor heterostructures.A unique advantage of this platform is that the quantum spin Hall edge state realized in inverted InAs/GaSb is a topologically protected spinless single mode,and can be tuned by front-back dual gates.Similar to a number of other platforms the proximity effect of a conventional s-wave superconductor on the helical edge has been proposed to realize Majorana bound state.We will present an introduction to this platform with a focus on the materials and devices aspects and those points that are particularly illustrative.

关键词： topological insulators heterostructures topological superconductivity molecular beam epitaxy electrical transport

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Pair density wave facilitated by Bloch quantum geometry in nearly flat band multiorbital superconductors

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 108-114页

作者： Weipeng Chen Wen Huang Shenzhen Institute for quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China International Quantum Academy Shenzhen 518048China Guangdong Provincial Key Laboratory of quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China

Bloch electrons in multiorbital systems carry quantum geometric information characteristic of their wavevector-dependent interorbital mixing.The geometric nature impacts electromagnetic responses,and this effect carries over to the superconducting state,which receives a geometric contribution to the superfluid weight.In this paper,we show that this contribution could become negative under certain appropriate circumstances.This may facilitate the stabilization of Cooper pairings with real space phase modulation,i.e.,the pair density wave order,as we demonstrate through two-orbital model Bogoliubov de-Gennes mean-field calculations.The quantum geometric effect therefore constitutes an intrinsic mechanism for the formation of such a novel phase of matter in the absence of external magnetic field.

关键词： superconductivity quantum geometry pair density wave superfluid weight FFLO

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Magneto optics and time resolved terahertz spectrocopy

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Chinese Physics B 2018年第7期27卷 112-119页

作者：董涛谌志国王楠林 international Center for quantum Materials School of Physics Peking University Institute of Physics Chinese Academy of Sciences

Exploring, manipulating, and understanding new exotic quantum phenomena in condensed-matter systems have gen- erated great interest in the scientific community. Static and time resolved optical spectroscopies after photoexcitations are important experimental tools for probing charge dynamics and quasiparticle excitations in quantum materials. In Syner- getic Extreme Condition User Facility （SECUF）, we shall construct magneto-infrared and terahertz measurement systems and develop a number of ultrafast femtosecond laser based systems, including intense near to mid-infrared pump terahertz probe. In this article, we shall describe several systems to be constructed and developed in the facilities, then present some examples explaining the application of magneto optics and time resolved spectroscopy techniques.

关键词： magneto-optics infrared spectroscopy mid-infrared pump terahertz probe

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Rare-earth quantum memories: The experimental status quo

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Frontiers of physics 2023年第2期18卷 161-179页

作者： Mucheng Guo Shuping Liu Weiye Sun Miaomiao Ren Fudong Wang Manjin Zhong Shenzhen Institute for quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China International Quantum Academy Shenzhen 518048China Guangdong Provincial Key Laboratory of quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China

Rare-earth doped crystals carry great prospect in developing ensemble-based solid state quantum memories for remote quantum communication and fast quantum processing applications. In recent years, with this system, remarkable quantum storage performances have been realized, and more exciting applications have been exploited, while the technical challenges are also significant. In this paper, we outlined the status quo in the development of rare-earth-based quantum memories from the point of view of different storage protocols, with a focus on the experimental demonstrations. We also analyzed the challenges and provided feasible solutions.

关键词： solid-state quantum memory rare-earth crystals quantum network quantum communication

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超越旋波近似的自旋轨道耦合拓扑费米子

Science Bulletin 2024年第6期69卷 747-755页

作者：张涵王文伟乔畅张龙梁明诚吴瑞王旭杰刘雄军张熙博 international Center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of quantum Matter Beijing 100871China School of Physics and Institute for quantum Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China Hefei National Laboratory Hefei 230088China Beijing academy of quantum Information Sciences Beijing 100193China International Quantum Academy Shenzhen 518048China

The realization of spin-orbit-coupled ultracold gases has driven a wide range of research and is typically based on the rotating wave approximation(RWA).By neglecting the counter-rotating terms,RWA characterizes a single near-resonant spin-orbit(SO)coupling in a two-level system.Here,we propose and experimentally realize a new scheme for achieving a pair of two-dimensional(2D)SO couplings for ultracold fermions beyond RWA.This work not only realizes the first anomalous Floquet topological Fermi gas beyond RWA,but also significantly improves the lifetime of the 2D-SO-coupled Fermi gas.Based on pump-probe quench measurements,we observe a deterministic phase relation between two sets of SO couplings,which is characteristic of our beyond-RWA scheme and enables the two SO couplings to be simultaneously tuned to the optimum 2D configurations.We observe intriguing band topology by measuring two-ring band-inversion surfaces,quantitatively consistent with a Floquet topological Fermi gas in the regime of high Chern numbers.Our study can open an avenue to explore exotic SO physics and anomalous topological states based on long-lived SO-coupled ultracold fermions.

关键词： Spin-orbit coupling Ultracold atoms Fermi gases quantum simulation Topological phases of matter

Realization of highly isolated stable few-spin systems based on alkaline-earth fermions

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Frontiers of physics 2023年第6期18卷 231-239页

作者： Wen-Wei Wang Han Zhang Chang Qiao Ming-Cheng Liang Rui Wu Xibo Zhang international Center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of quantum Matter Beijing 100871China Beijing academy of quantum Information Sciences Beijing 100193China Hefei National Laboratory Hefei 230088China

Few-level systems consisting of a certain number of spin states have provided the basis of a wide range of cold atom researches.However,more developments are still needed for better preparation of isolated few-spin systems.In this work,we demonstrate a highly nonlinear spin-discriminating(HNSD)method for isolating an arbitrary few-level manifold out of a larger total number of spin ground states in fermionic alkaline-earth atoms.With this method,we realize large and tunable energy shifts for unwanted spin states while inducing negligible shifts for the spin states of interest,which leads to a highly isolated few-spin system under minimal perturbation.Furthermore,the isolated few-spin system exhibits a long lifetime on the hundred-millisecond scale.Using the HNSD method,we demonstrate a characteristic Rabi oscillation between the two states of an isolated two-spin Fermi gas.Our method has wide applicability for realizing long-lived two-spin or high-spin quantum systems based on alkaline-earth fermions.

关键词： few-spin system alkaline-earth atoms ultracold Fermi gas a.c.Stark shift long-lived quantum system