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Realization of -bit semiclassical quantum Fourier transform on IBM's quantum cloud computer

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Chinese Physics B 2019年第2期28卷 117-122页

作者： Xiang-Qun Fu Wan-Su Bao He-Liang Huang Tan Li Jian-Hong Shi Xiang Wang Shuo Zhang Feng-Guang Li Henan Key Laboratory of quantum Information and Cryptography Information Engineering University Synergetic Innovation center of quantum Information and quantum Physics University of Science and Technology of China

To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z_(2~3) on IBM's quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the *** squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N = 15 is successfully factorized by implementing Shor's algorithm.

关键词： quantum cloud computation quantum Fourier transform semiclassical quantum Fourier transform Shor’s algorithm

Correlation-enhanced electron-phonon coupling for accurate evaluation of the superconducting transition temperature in bulk FeSe

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Science China(Physics,Mechanics & Astronomy) 2022年第6期65卷 131-136页

作者： Wenjun Ding Yilin Wang Tong Wei Jiaqing Gao Ping Cui Zhenyu Zhang International center for quantum Design of Functional Materials(ICQD) Hefei National Laboratory for Physical Sciences at the Microscaleand CAS Center for Excellence in Quantum Information and Quantum PhysicsUniversity of Science and Technology of ChinaHefei 230026China

It has been widely recognized that,based on standard density functional theory calculations of the electron-phonon coupling,the superconducting transition temperature(T_(c))in bulk FeSe is exceptionally low(almost 0 K)within the Bardeen-Cooper-Schrieffer *** the experimentally observed T_(c)is much higher(∼10 K),and the underlying physical origin remains to be fully explored,especially at the quantitative *** we present the first accurate determination of T_(c)in FeSe where the correlation-enhanced electron-phonon coupling is treated within first-principles dynamical mean-field *** studies treat both the multiple electronic bands across the Fermi level and phononic bands,and reveal that all the optical phonon modes are effectively coupled with the conduction electrons,including the important contributions of a single breathing mode as established by previ-ous ***,each of those phonon modes contributes pronouncedly to the electron pairing,and the resultant T_(c)is drastically enhanced to the experimentally observed *** approach developed here should be broadly applicable to other superconducting systems where correlation-enhanced electron-phonon coupling plays an important role.

关键词： bulk FeSe superconductivity correlation-enhanced electron-phonon coupling density functional theory dynamical mean-field theory

Observation of 1D Fermi arc states in Weyl semimetal TaAs

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National Science Review 2022年第8期9卷 62-70页

作者： Xiaohu Zheng Qiangqiang Gu Yiyuan Liu Bingbing Tong Jian-Feng Zhang Chi Zhang Shuang Jia Ji Feng Rui-Rui Du International center for quantum Materials School of PhysicsPeking University Collaborative Innovation center of quantum Matter State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences CAS center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences Beijing Academy of quantum Information Sciences

Fermi arcs on Weyl semimetals exhibit many exotic quantum phenomena. Usually found on atomically flat surfaces with approximate translation symmetry, Fermi arcs are rooted in the peculiar topology of bulk Bloch bands of 3D crystals. The fundamental question of whether a 1D Fermi arc can be probed remains unanswered. Such an answer could significantly broaden potential applications of Weyl semimetals. Here,we report a direct observation of robust edge states on atomic-scale ledges in TaAs using low-temperature scanning tunneling microscopy/spectroscopy. Spectroscopic signatures and theoretical calculations reveal that the 1D Fermi arcs arise from the chiral Weyl points of bulk crystals. The crossover from 2D Fermi arcs to eventual complete localization on 1D edges was arrested experimentally on a sequence of surfaces. Our results demonstrate extreme robustness of the bulk-boundary correspondence, which offers topological protection for Fermi arcs, even in cases in which the boundaries are at the atomic-scale. The persistent 1D Fermi arcs can be profitably exploited in miniaturized quantum devices.

关键词： Weyl semimetals Fermi arc edge states chiral Weyl points TaAs scanning tunneling microscopy/spectroscopy

Semiconductor quantum computation

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National Science Review 2019年第1期6卷 32-54页

作者： Xin Zhang Hai-Ou Li Gang Cao Ming Xiao Guang-Can Guo Guo-Ping Guo Key Laboratory of quantum Information CAS University of Science and Technology of China Synergetic Innovation center of quantum Information & quantum Physics University of Science and Technology of China

Semiconductors, a significant type of material in the information era, are becoming more and more powerful in the field of quantum information. In recent decades, semiconductor quantum computation was investigated thoroughly across the world and developed with a dramatically fast speed. The research varied from initialization, control and readout of qubits, to the architecture of fault-tolerant quantum ***, we first introduce the basic ideas for quantum computing, and then discuss the developments of single-and two-qubit gate control in semiconductors. Up to now, the qubit initialization, control and readout can be realized with relatively high fidelity and a programmable two-qubit quantum processor has even been demonstrated. However, to further improve the qubit quality and scale it up, there are still some challenges to resolve such as the improvement of the readout method, material development and scalable designs. We discuss these issues and introduce the forefronts of progress. Finally, considering the positive trend of the research on semiconductor quantum devices and recent theoretical work on the applications of quantum computation, we anticipate that semiconductor quantum computation may develop fast and will have a huge impact on our lives in the near future.

关键词： semiconductor quantum dot qubit quantum computation spin manipulation

Liquid-liquid phase transition in water

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Science China(Physics,Mechanics & Astronomy) 2014年第5期57卷 810-818页

作者： SUN ZhaoRu SUN Gang CHEN YiXuan XU LiMei International center for quantum Materials Peking University

Water shows anomalies different from most of other *** sceniaros have been proposed to explain water anomalies,among which the liquid-liquid phase transition(LLPT)is the most discussed *** attributes water anomalies to the existence of a hypothesized liquid-liquid critical point(LLCP)buried deep in the supercooled *** briefly review the recent experimental and theoretical progresses on the study of the LLPT in *** studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical *** results of different water models for LLPT and the experimental evidence in confined water are also discussed.

关键词： liquid-liquid phase transition liquid-liquid critical point water anomalies

Magnetic flux control of chiral Majorana edge modes in topological superconductor

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Science China(Physics,Mechanics & Astronomy) 2018年第12期61卷 89-94页

作者： Yan-Feng Zhou Zhe Hou Peng Lv XinCheng Xie Qing-Feng Sun International center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation center of quantum Matter Beijing 100871China CAS center for Excellence in Topological quantum Computation University of Chinese Academy of SciencesBeijing 100190China

We study the transport of chiral Majorana edge modes(CMEMs) in a hybrid quantum anomalous Hall insulator-topological superconductor(QAHI-TSC) system in which the TSC region contains a Josephson junction and a cavity. The Josephson junction undergoes a topological transition when the magnetic flux through the cavity passes through half-integer multiples of magnetic flux quantum. For the trivial phase, the CMEMs transmit along the QAHI-TSC interface as without magnetic flux. However, for the nontrivial phase, a zero-energy Majorana state appears in the cavity, leading to that a CMEM can resonantly tunnel through the Majorana state to a different CMEM. These findings may provide a feasible scheme to control the transport of CMEMs by using the magnetic flux and the transport pattern can be customized by setting the size of the TSC.

关键词： Majorana fermions Josephson junction topological superconductor non-equilibrium Green's function

Dissipative preparation of multipartite Greenberger-Horne-Zeilinger states of Rydberg atoms

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Chinese Physics B 2021年第2期30卷 71-78页

作者： Chong Yang Dong-Xiao Li Xiao-Qiang Shao center for quantum Sciences and School of Physics Northeast Normal UniversityChangchun 130024China center for Advanced Optoelectronic Functional Materials Research and Key Laboratory for UV Light-Emitting Materials and Technology of Ministry of EducationNortheast Normal UniversityChangchun 130024China School of Physics International Joint Laboratory on Quantum Sensing and Quantum MetrologyHuazhong University of Science and TechnologyWuhan 430074China

The multipartite Greenberger-Horne-Zeilinger(GHZ)states play an important role in large-scale quantum information *** utilize the polychromatic driving fields and the engineered spontaneous emissions of Rydberg states to dissipatively drive three-and four-partite neutral atom systems into the steady GHZ states,at the presence of the nextnearest neighbor interaction of excited Rydberg ***,the introduction of quantum Lyapunov control can help us optimize the dissipative dynamics of the system so as to shorten the convergence time of the target state,improve the robustness against the spontaneous radiations of the excited Rydberg states,and release the limiting condition for the strengths of the polychromatic driving *** the feasible experimental conditions,the fidelities of three-and four-partite GHZ states can be stabilized at 99.24%and 98.76%,respectively.

关键词： multipartite entanglement Lyapunov control Rydberg antiblockade quantum dissipation

Lorentz quantum computer

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Chinese Physics B 2023年第4期32卷 175-183页

作者：何文昊王朕铎吴飙 International center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Wilczek quantum center School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation center of quantum Matter Beijing 100871China

A theoretical model of computation is proposed based on Lorentz quantum *** the standard qubits,this model has an additional bit,which we call hyperbolic bit(or hybit in short).A set of basic logical gates are constructed and their universality is *** an application,a search algorithm is designed for this computer model and is found to be exponentially faster than Grover's search algorithm.

关键词： quantum computing Lorentz quantum mechanics Grover search

Anomalous Hall effect in ferromagnetic Weyl semimetal candidate Zr1-x VxCo1.6Sn

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Chinese Physics B 2020年第7期29卷 204-210页

作者： Guangqiang Wang Zhanghao Sun Xinyu Si Shuang Jia International center for quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation center of quantum Matter Beijing 100871China CAS center for Excellence in Topological quantum Computation University of Chinese Academy of SciencesBeijing 100190China Beijing Academy of quantum Information Sciences Beijing 100193

We grew single crystals of vanadium-substituted,ferromagnetic Weyl semimetal candidate Zr1-xVxCo1.6Sn from molten tin *** solid solutions all crystallize in a full Heusler structure(L21)while their Curie temperatures and magnetic moments are enhanced by *** resistivity gradually changes from bad-metal-like to semiconductor-like with increasing x while the anomalous Hall effect(AHE),which can be well fitted by Tian-Ye-Jin(TYJ)scaling,[1]is also ***,we find an apparent electron-electron interaction(EEI)induced quantum correction in resistivity at low *** anomalous Hall conductivity(AHC)dominated by the intrinsic term is not corrected.

关键词： anomalous Hall effect ferromagnetic Weyl semimetal full Heusler electron-electron interaction