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Proposal for sequential Stern-Gerlach experiment with programmable quantum processors

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Chinese physics B 2024年第2期33卷 131-136页

作者：胡孟军缪海兴张永生 Beijing Academy of quantum Information Sciences Beijing 100193China State Key laboratory of Low Dimensional quantum physics Department of PhysicsTsinghua UniversityBeijing 100084China laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China Synergetic Innovation Center of quantum Information and quantum physics University of Science and Technology of ChinaHefei 230026China Hefei National laboratory University of Science and Technology of ChinaHefei 230088China

The historical significance of the Stern–Gerlach(SG)experiment lies in its provision of the initial evidence for space *** time,its sequential form has evolved into an elegant paradigm that effectively illustrates the fundamental principles of quantum *** date,the practical implementation of the sequential SG experiment has not been fully *** this study,we demonstrate the capability of programmable quantum processors to simulate the sequential SG *** specific parametric shallow quantum circuits,which are suitable for the limitations of current noisy quantum hardware,are given to replicate the functionality of SG devices with the ability to perform measurements in different ***,it has been demonstrated that Wigner’s SG interferometer can be readily implemented in our sequential quantum *** the utilization of the identical circuits,it is also feasible to implement Wheeler’s delayed-choice *** propose the utilization of cross-shaped programmable quantum processors to showcase sequential experiments,and the simulation results demonstrate a strong alignment with theoretical *** the rapid advancement of cloud-based quantum computing,such as BAQIS Quafu,it is our belief that the proposed solution is well-suited for deployment on the cloud,allowing for public *** findings not only expand the potential applications of quantum computers,but also contribute to a deeper comprehension of the fundamental principles underlying quantum theory.

关键词： sequential Stern-Gerlach quantum circuit quantum processor

Experimental observation of spontaneous symmetry breaking in a quantum phase transition

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Science China(physics,Mechanics & Astronomy) 2024年第2期67卷 34-39页

作者： Wen Ning Ri-Hua Zheng Jia-Hao Lu Fan Wu Zhen-Biao Yang Shi-Biao Zheng Fujian Key laboratory of quantum Information and quantum Optics College of Physics and Information EngineeringFuzhou UniversityFuzhou 350108China Hefei National laboratory Hefei 230088China

Spontaneous symmetry breaking(SSB)plays a central role in understanding a large variety of phenomena associated with phase transitions,such as superfluid and *** far,the transition from a symmetric vacuum to a macroscopically ordered phase has been substantially *** process bridging these two distinct phases is critical to understanding how a classical world emerges from a quantum phase transition,but so far remains unexplored in *** here report an experimental demonstration of such a process with a quantum Rabi model engineered with a superconducting *** move the system from the normal phase to the superradiant phase featuring two symmetry-breaking field components,one of which is observed to emerge as the classical *** results demonstrate that the environment-induced decoherence plays a critical role in the SSB.

关键词： quantum phase transition Rabi model spontaneous symmetry breaking superconducting circuit Schrodinger cat states

Purification of copper foils driven by single crystallization

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Chinese physics B 2024年第2期33卷 506-511页

作者：寇金宗赵孟泽李兴光何梦林杨方友刘科海成庆秋任云龙刘灿付莹吴慕鸿刘开辉王恩哥 Songshan Lake Materials laboratory Dongguan 523808China Beijing National laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Guangdong Provincial Key laboratory of quantum Engineering and quantum Materials School of PhysicsSouth China Normal UniversityGuangzhou 510006China Guangdong–Hong Kong Joint laboratory of quantum Matter Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China State Key laboratory for Mesoscopic physics Frontiers Science Center for Nano-optoelectronicsSchool of PhysicsPeking UniversityBeijing 100871China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Department of PhysicsRenmin University of ChinaBeijing 100872China International Center for quantum Materials Collaborative Innovation Center of Quantum MatterPeking UniversityBeijing 100871China School of physics Liaoning UniversityShenyang 110036China

High-purity copper(Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9%(3N) to 99.99%(4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of *** success of purification mainly relies on(i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and(ii) the high-temperature evaporation of elements with high saturated vapor *** purified Cu foils display higher flexibility(elongation of 70%) and electrical conductivity(104% IACS) than that of the original commercial rolled Cu foils(elongation of 10%, electrical conductivity of ~ 100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

关键词： purification copper foil thermal annealing technique single crystallization

Lorentz violation induces isospectrality breaking in Einstein-bumblebee gravity theory

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Science China(physics,Mechanics & Astronomy) 2024年第8期67卷 87-96页

作者： Wentao Liu Xiongjun Fang Jiliang Jing Jieci Wang Department of physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

In this study,we investigate the quasinormal modes(QNMs)of a Lorentz-violating spacetime,factoring in a cosmological constant,within the framework of Einstein-bumblebee *** findings reveal that the interaction of spacetime with an anisotropic bumblebee field imparts distinct contributions to the axial and polar sectors of the vector *** subsequently breaks the isospectrality typically observed in vector *** evidence strongly indicates isospectral breaking in the vector modes of Einstein-bumblebee black holes:a pronounced breakage in the real part of the frequencies,while the imaginary component seems less *** isospectral breaking indicates the existence of two different waveforms in the Ringdown phase of the black hole,which provides a potential signal of quantum gravity observable in current experiments.

关键词： Lorentz-violating isospectral breaking quasinormal modes

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Gravitational wave fluxes on generic orbits in near-extreme Kerr spacetime:Higher spin and large eccentricity

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Science China(physics,Mechanics & Astronomy) 2024年第11期67卷 16-28页

作者： Changkai Chen Jiliang Jing Department of physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

To accurately obtain the waveform template of gravitational waves, substantial computational resources and extremely high precision are often required. In a previous study, we employed the confluent Heun function to obtain an exact solution to the Teukolsky equation. This approach allowed us to efficiently and accurately calculate the gravitational wave flux for a particle in circular orbits around a Schwarzschild black hole. Building on this method, we now extend its application to calculate the asymptotic gravitational wave fluxes from a particle in generic orbits around a near-extreme Kerr black hole. Our extended method proves particularly effective in handling computational challenges associated with large eccentricities(e = 0.9), higher spins(a = 0.999), higher harmonic modes, and strong-field regions. The results we obtained significantly outperform those derived from the numerical integration method based on the Mano-Suzuki-Takasugi method.

关键词： gravitational wave fluxes exact solution Teukolsky equation near-extreme Kerr black hole

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Security analysis of satellite-to-ground reference-frame-independent quantum key distribution with beam wandering

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Chinese physics B 2024年第8期33卷 192-201页

作者：周淳赵燕美杨晓亮陆宜飞周雨姜晓磊汪海涛汪洋李家骥江木生汪翔张海龙李宏伟鲍皖苏 Henan Key laboratory of quantum Information and Cryptography SSF IEUZhengzhou 450001China Synergetic Innovation Centre of quantum Information and quantum physics University of Science and Technology of ChinaHefei 230026China

The reference-frame-independent(RFI)quantum key distribution(QKD)is suitable for satellite-based links by removing the active alignment on the reference ***,how the beam wandering influences the performance of RFI-QKD remains a pending issue in satellite-to-ground *** this paper,based on the mathematical model for characterizing beam wandering,we present the security analysis for satellite-to-ground RFI-QKD and analytically derive formulas for calculating the secret key rate with beam *** simulation results show that the performance of RFI-QKD is better than the Bennett–Brassard 1984(BB84)QKD with beam wandering in asymptotic ***,the degree of influences of beam wandering is specifically presented for satellite-to-ground RFI-QKD when statistical fluctuations are taken into *** work can provide theoretical support for the realization of RFI-QKD using satellite-to-ground links and have implications for the construction of large-scale satellite-based quantum networks.

关键词： quantum key distribution satellite-to-ground beam wandering

Chiral bound states in a staggered array of coupled resonators

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Chinese physics B 2024年第2期33卷 124-130页

作者：金伍林李静卢竞龚志瑞周兰 Synergetic Innovation Center for quantum Effects and Applications Key Laboratory for Matter Microstructure and Function of Hunan ProvinceKey Laboratory of Low-Dimensional Quantum Structures and Quantum Control of the Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesXiangjiang-Laboratory and Department of PhysicsHunan Normal UniversityChangsha 410081China College of physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China

We study the chiral bound states in a coupled-resonator array with staggered hopping strengths,which interacts with a two-level small atom through a single coupling point or two adjacent *** addition to the two typical bound states found above and below the energy bands,this system presents an extraordinary chiral bound state located within the energy *** use the chirality to quantify the breaking of the mirror *** find that the chirality value undergoes continuous changes by tuning the coupling *** preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array,but also by the coherence between the two coupling *** the case with one coupling point,the chirality values varies monotonously with difference between the intracell hopping and the intercell *** in the case with two coupling points,due to the coherence between the two coupling points the perfect chiral states can be obtained.

关键词： bound states two-level small atom coupled-resonator array chirality

Effect of the mixing of s-wave and chiral p-wave pairings on electrical shot noise properties of normal metal/superconductor tunnel junctions

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Chinese physics B 2024年第7期33卷 538-545页

作者：胡雨辰胡梁宾 Guangdong Provincial Key laboratory of quantum Engineering and quantum Materials School of PhysicsSouth China Normal UniversityGuangzhou 510631China

We study theoretically the electrical shot noise properties of tunnel junctions between a normal metal and a superconductor with the mixture of singlet s-wave and chiral triplet p-wave pairing due to broken inversion symmetry. We investigate how the shot noise properties vary as the relative amplitude between the two parity components in the pairing potential is changed. It is demonstrated that some characteristics of the electrical shot noise properties of such tunnel junctions may depend sensitively on the relative amplitude between the two parity components in the pairing potential, and some significant changes may occur in the electrical shot noise properties when the relative amplitude between the two parity components is varied from the singlet s-wave pairing dominated regime to the chiral triplet p-wave pairing dominated regime. In the chiral triplet p-wave pairing dominated regime, the ratio of noise power to electric current is close to 2e both in the in-gap and in the out-gap region. In the singlet s-wave pairing dominated regime, the value of this ratio is close to 4e in the inner gap region but may reduce to about 2e in the outer gap region as the relative amplitude of the chiral triplet pairing component is increased. The variations of the differential shot noise with the bias voltage also exhibit some significantly different features in different regimes. Such different features can serve as useful diagnostic tools for the determination of the relative magnitude of the two parity components in the pairing potential.

关键词： normal metal/superconductor tunnel junctions shot noise mixing of s-wave and chiral p-wave pairing spin–orbit coupling

Orbital-Ordering Driven Simultaneous Tunability of Magnetism and Electric Polarization in Strained Monolayer VCl_(3)

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Chinese physics Letters 2024年第4期41卷 126-131页

作者：郭的坪王聪王侣锦陆赟豪吴骅张妍宁季威 Beijing Key laboratory of Optoelectronic Functional Materials&Micro-Nano devices Department of PhysicsRenmin University of ChinaBeijing 100872China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Renmin University of ChinaBeijing 100872China Zhejiang Province Key laboratory of quantum Technology and device State Key Laboratory of Silicon MaterialsDepartment of PhysicsZhejiang UniversityHangzhou 310027China laboratory for Computational Physical Sciences(MOE) State Key Laboratory of Surface Physicsand Department of PhysicsFudan UniversityShanghai 200433China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu 610054China

Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic *** predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally *** theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground *** first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are *** atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase *** doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane *** can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under *** establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).

关键词： monolayer symmetry orbital