Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical...Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.展开更多
The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic f...The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.展开更多
We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-M...We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.展开更多
The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance ima...The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance imaging(MRI).Herein,the fabrication of superconducting joints using reacted carbon-doped multifilament MgB_(2)wires for MRI magnets is reported.To achieve successful superconducting joints,the powder-in-mold method was employed,which involved tuning the filament protection mechanism,the powder compaction pressure,and the heat treatment condition.The fabricated joints demonstrated clear superconducting-to-normal transitions in self-field,with effective magnetic field screening up to 0.5 T at 20 K.To evaluate the interface between one of the MgB_(2)filaments and the MgB_(2)bulk within the joint,serial sectioning was conducted for the first time in this type of superconducting joint.The serial sectioning revealed space formation at the interface,potentially caused by the volume shrinkage associated with the MgB_(2)formation or the combined effect of the volume shrinkage and the different thermal expansion coefficients of the MgB_(2)bulk,the filament,the mold,and the sealing material.These findings are expected to be pivotal in developing MgB_(2)superconducting joining technology for MRI magnet applications through interface engineering.展开更多
Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting app...Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting applications.With respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic fields.Traditional numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally demanding.Herein,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake coils.This approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic scale.We then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic scale.The results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and efficient.The proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.展开更多
Non-Hermitian dissipation dynamics,capable of turning the conventionally detrimental decoherence effects to useful resources for state engineering,is highly attractive to quantum information processing.In this work,an...Non-Hermitian dissipation dynamics,capable of turning the conventionally detrimental decoherence effects to useful resources for state engineering,is highly attractive to quantum information processing.In this work,an effective scheme is developed for implementing fast population transfer with a superconducting qutrit via the non-Hermitian shortcut to adiabaticity(STA).We first deal with aΛ-configuration interaction between the qutrit and microwave drivings,in which the dephasing-assisted qubit state inversion requiring an overlarge dephasing rate is constructed non-adiabatically.After introducing a feasible ancillary driving that directly acts upon the qubit states,the target state transfer can be well realized but with an accessible qubit dephasing rate.Moreover,a high fidelity could be numerically obtained in the considered system.The strategy could provide a new route towards the non-Hermitian shortcut operations on superconducting quantum circuits.展开更多
High-pressure structural search was performed on the hydrogen-rich compound LuBeH8at pressures up to 200 GPa.We found an Fm3m structure that exhibits stability and superconductivity above 100 GPa.Our phonon dispersion...High-pressure structural search was performed on the hydrogen-rich compound LuBeH8at pressures up to 200 GPa.We found an Fm3m structure that exhibits stability and superconductivity above 100 GPa.Our phonon dispersion,electronic band structure,and superconductivity analyses in the 100–200 GPa pressure range reveal a strong electron–phonon coupling in Lu Be H8,while the superconducting critical temperature Tcshows a decreasing trend as the pressure increases,with T_(c)=255 K at 200 GPa and maximal T_(c)=355 K at 100 GPa.This study demonstrated the room-temperature superconductivity in Fm3m thus enriching the family of ternary hydrides.These findings provide valuable guidance for identifying new high-temperature superconducting hydrides.展开更多
On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorab...On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.展开更多
Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers wit...Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers with its outstanding current-carrying capacity and mechanical properties.The REBCO tapes are wound spirally on the surface of CORC cable.Under extreme loadings,the REBCO tapes with layered composite structures are vulnerable,which can lead to degradation of critical current and even quenching of superconducting devices.In this paper,we simulate the deformation of CORC cable under external loads,and analyze the damage inside the tape with the cohesive zone model(CZM).Firstly,the fabrication and cabling of CORC are simulated,and the stresses and strains generated in the tape are extracted as the initial condition of the next step.Then,the tension and bending loads are applied to CORC cable,and the damage distribution inside the tape is presented.In addition,the effects of some parameters on the damage are discussed during the bending simulations.展开更多
An ultrafast pump-probe spectroscopy system combined with a cryogenic diamond anvil cell(DAC) instrument is developed to investigate the photo-excitation dynamic properties of condensed materials under low temperature...An ultrafast pump-probe spectroscopy system combined with a cryogenic diamond anvil cell(DAC) instrument is developed to investigate the photo-excitation dynamic properties of condensed materials under low temperature and high pressure(LTHP) conditions.The ultrafast dynamics study is performed on Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi-2212) thin film under LTHP conditions.The superconducting(SC) phase transition has been observed by analyzing the ultrafast dynamics of Bi-2212 as a function of pressure and temperature.Our results suggest that the pump-probe spectroscopy system combined with a cryogenic DAC instrument is an effective method to study the physical mechanism of condensed matter physics at extreme conditions,especially for the SC phase transition.展开更多
Photonic crystal structures have excellent optical properties,so they are widely studied in conventional optical materials.Recent research shows that high-temperature superconducting periodic structures have natural p...Photonic crystal structures have excellent optical properties,so they are widely studied in conventional optical materials.Recent research shows that high-temperature superconducting periodic structures have natural photonic crystal features and they are favourable candidates for single-photon detection.Considering that superconductors have completely different properties from conventional optical materials,we study the energy level diagram and mid-infrared 3μm–5μm transmission spectrum of two-dimensional superconducting photonic crystals in both superconducting and quenched states with the finite element method.The energy level diagram of the circular crystal column superconducting structure shows that the structure has a large band gap width in both states.At the same fill factor,the circular crystal column superconducting structure has a larger band gap width than the others structures.For lattice structures,the zero transmission point of the square lattice structure is robust to the incident angle and environmental temperature.Our research has guiding significance for the design of new material photonic crystals,photon modulation and detection.展开更多
The precise control and manipulation of the qubit state are vital for quantum simulation and quantum computation.In superconducting circuits,one notorious error comes from the crosstalk of microwave signals applied to...The precise control and manipulation of the qubit state are vital for quantum simulation and quantum computation.In superconducting circuits,one notorious error comes from the crosstalk of microwave signals applied to different qubit control lines.In this work,we present a method for the calibration and cancellation of the microwave crosstalk and experimentally demonstrate its effectiveness in a superconducting 10-qubit chain.The method is convenient and efficient especially for calibrating the microwave crosstalk with large amplitudes and variations,which can be performed successively to reduce the microwave crosstalk by two to three orders.The qubit chain with microwave driving is governed by one-dimensional(1D)Bose-Hubbard model in transverse field,which is nonintegrable and shows thermalization behaviour during the time evolution from certain initial states.Such thermalization process is observed with excellent agreement between experiment and theory further confirming the effective global cancellation of the microwave crosstalk.展开更多
Quantum many-body systems in which time-reversal symmetry is broken give rise to a wealth of exotic phases,and thus constitute one of the frontiers of modern condensed matter physics.Quantum simulation allows us to be...Quantum many-body systems in which time-reversal symmetry is broken give rise to a wealth of exotic phases,and thus constitute one of the frontiers of modern condensed matter physics.Quantum simulation allows us to better understand many-body systems with huge Hilbert space,where classical simulation is usually inefficient.With superconducting quantum circuit as a platform for quantum simulation,we realize synthetic Abelian gauge fields by using microwave drive and tunable coupling in loop configurations to break the time-reversal symmetry of the system.Based on high-precision manipulation and readout of circuit-QED architecture,we demonstrate the chiral ground spin current of a time-reversal symmetry broken system with nontrivial interactions.Our work is a significant attempt to simulate quantum many-body systems with time-reversal symmetry breaking in multi-qubit superconducting processors.展开更多
A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet dur...A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.展开更多
The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this sy...The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this system are investigated using the two-band Ginzburg-Landau theory.We calculate the temperature dependence of upper critical field in arbitrary direction and critical supercurrent density through the FeSe film.It is revealed that the normalized upper critical field is independent of the film thickness and all of our theoretical results are in accordance with the experimental data.These thus strongly indicate the existence of two-gap s-wave superconductivity in this material.展开更多
Discovering new superconductors via traditional trial-and-error experimental approaches is apparently a time-consuming process,and the correlations between the critical temperature(Tc) and material features are still ...Discovering new superconductors via traditional trial-and-error experimental approaches is apparently a time-consuming process,and the correlations between the critical temperature(Tc) and material features are still obscure.The rise of machine learning(ML) technology provides new opportunities to speed up inefficient exploration processes,and could potentially uncover new hints on the unclear correlations.In this work,we utilize open-source materials data,ML models,and data mining methods to explore the correlation between the chemical features and Tcvalues of superconducting materials.To further improve the prediction accuracy,a new model is created by integrating three basic algorithms,showing an enhanced accuracy with the coefficient of determination(R2) score of 95.9 % and root mean square error(RMSE) of 6.3 K.The average marginal contributions of material features towards Tcvalues are estimated to determine the importance of various features during prediction processes.The results suggest that the range thermal conductivity plays a critical role in Tcprediction among all element features.Furthermore,the integrated ML model is utilized to screen out potential twenty superconducting materials with Tcvalues beyond 50.0 K.This study provides insights towards Tcprediction to accelerate the exploration of potential high-Tcsuperconductors.展开更多
In quantum computation and quantum information processing, the manipulation and engineering of quantum systems to suit certain purposes are an ongoing task. One such example is quantum state transfer(QST), an essentia...In quantum computation and quantum information processing, the manipulation and engineering of quantum systems to suit certain purposes are an ongoing task. One such example is quantum state transfer(QST), an essential requirement for both quantum communication and large-scale quantum computation. Here we engineer a chain of four superconducting qubits with tunable couplers to realize the perfect state transfer(PST) protocol originally proposed in quantum spin networks and successfully demonstrate the efficient transfer of an arbitrary single-qubit state from one end of the chain to the other,achieving a high fidelity of 0.986 in just 25 ns. This demonstrated QST is readily to extend to larger chain and multi-node configurations, thus serving as a desirable tool for scalable quantum information processing.展开更多
In this paper,we present observations of free oscillations of the Earth after major earthquakes in Chile(February 27,2010,Mw8.8)and Japan(March 11,2011,Mw9.1)using data from the dual-sphere superconducting gravimeter(...In this paper,we present observations of free oscillations of the Earth after major earthquakes in Chile(February 27,2010,Mw8.8)and Japan(March 11,2011,Mw9.1)using data from the dual-sphere superconducting gravimeter(SG-055),installed at Badargadh(23°0.47 N,70°0.62 E),Kutch,Gujarat,India in March 2009.To see the noise characteristics,we calculated the power spectral density of the gravity time series of 5 quiet days in the frequency band 0.05-20 mHz using the new low noise model(NLNM)as a reference.We compared the noise level of the Badargadh site to other SG sites around the world.This shows that the Badargadh SG is in a low noise state.We find that the noise increases at frequencies below 1 mHz.Such a characteristic is also observed in Djougou(Afrique,Benin)and Strasbourg(France).Using theoretical tides for Gujarat,we estimated a scale factor of about-814 nm/s~2/V for Gravl(lowersphere)and about-775 nm/s~2/V for Grav2(upper-sphere).We corrected the influence of atmospheric pressure from the one-second gravity data before switching to the frequency domain.We extracted a total of 53 Earth’s Free Oscillations(EFO)modes during the earthquake in Japan and about 47 EFO modes during the earthquake in Chile.We are able to extract the lowest0S2spheroidal mode(0.30945 mHz or54 min)and0S0radial mode(0.81439 mHz or 20 min).The longer time series shows individual0S2singlets and0S3(0.46855 mHz)singlets due to the Coriolis splitting effect.We cross-referenced the frequencies of these modes using the PREM model and previous global observations.The correlation coefficient between the observed and the PREM model for these two events are 0.999 for Japan earthquake and 0.993 for Chile earthquake.This validates the quality of the data useful for low-frequency studies in seismology.We also calculated the relative deviations of our observed fundamental modes with previously determined observed and theoretical values.We found that the relative deviations of our observed free oscillations do not exceed 0.5%,indicating good correlations.展开更多
Quantum entanglement, a key resource in quantum information processing, is reduced by interaction between the quantum system concerned and its unavoidable noisy environment. Therefore it is of particular importance to...Quantum entanglement, a key resource in quantum information processing, is reduced by interaction between the quantum system concerned and its unavoidable noisy environment. Therefore it is of particular importance to study the dynamical properties of entanglement in open quantum systems. In this work, we mainly focus on two qubits coupled to an adjustable environment, namely a semi-infinite transmission line. The two qubits' relaxations, through individual channels or collective channel or both, can be adjusted by the qubits' transition frequencies. We examine entanglement dynamics in this model system with initial Werner state, and show that the phenomena of entanglement sudden death and revival can be observed. Due to the hardness of preparing the Werner state experimentally, we introduce a new type of entangled state called pseudo-Werner state, which preserves as much entangling property as the Werner state, and more importantly,it is experiment friendly. Furthermore, we provide detailed procedures for generating pseudo-Werner state and studying entanglement dynamics with it, which can be straightforwardly implemented in a superconducting waveguide quantum electrodynamics system.展开更多
In this study,a phenomenological model of the radio frequency(RF)behavior of a superconducting cavity fundamental power coupler is proposed by analyzing the simulation results of a transient beam-loading process in an...In this study,a phenomenological model of the radio frequency(RF)behavior of a superconducting cavity fundamental power coupler is proposed by analyzing the simulation results of a transient beam-loading process in an extremely overcoupled superconducting cavity.Using this phenomenological model,the calculation of the transient reflected power from a superconducting cavity under beam loading can be mathematically simplified to algebraic operations without solving the differential equation governing the transient beam-loading process,while maintaining the calculation accuracy.Moreover,this phenomenological model can facilitate an intuitive understanding of the significant surge in the time evolution of reflected power from a superconducting cavity in certain beam-loading processes.The validity of this phenomenological model was carefully examined in various beam-loading processes and cavity conditions,and the method based on this phenomenological model was utilized in the transient RF analysis of the superconducting cavity system of the CAFe Linac,achieving satisfactory results.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11925304 and 12020101002)the Chinese Academy of Sciences Program(Grant No.GJJSTD20210002).
文摘Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.
基金This work is funded by the Magnetic Resonance Union of the Chinese Academy of Sciences(Grant No.2021gzl002)the International Partnership Program of Chinese Academy of Sciences(Grant No.182111KYSB20210014)+1 种基金the National Science Foundation of China(Grant No.52293423,Grant No.52277031)the Research and Development of Key Technologies and Equipment for Major Science and Technology Infrastructure of Development and Reform Commission of Shenzhen Municipality,China(Grant No.ZDKJ20190305002).
文摘The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.
基金Project supported by Beijing Natural Science Foundation (Grant No.Z200005)the National Key R&D Program of China (Grant Nos.2018YFE0202600 and 2022YFA1403800)+1 种基金the National Natural Science Foundation of China (Grant No.12274459)Beijing National Laboratory for Condensed Matter Physics,and Collaborative Research Project of Laboratory for Materials and Structures,Institute of Innovative Research,Tokyo Institute of Technology。
文摘We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.
基金the Japan Society for the Promotion of Science(JSPS)KAKENHI Grant Number JP18F18714Cryogenic Station,Research Network and Facility Services Division,National Institute for Materials Science(NIMS),Japansupported by the ARC Linkage Project(LP200200689)。
文摘The development of superconducting joining technology for reacted magnesium diboride(MgB_(2))conductors remains a critical challenge for the advancement of cryogen-free MgB_(2)-based magnets for magnetic resonance imaging(MRI).Herein,the fabrication of superconducting joints using reacted carbon-doped multifilament MgB_(2)wires for MRI magnets is reported.To achieve successful superconducting joints,the powder-in-mold method was employed,which involved tuning the filament protection mechanism,the powder compaction pressure,and the heat treatment condition.The fabricated joints demonstrated clear superconducting-to-normal transitions in self-field,with effective magnetic field screening up to 0.5 T at 20 K.To evaluate the interface between one of the MgB_(2)filaments and the MgB_(2)bulk within the joint,serial sectioning was conducted for the first time in this type of superconducting joint.The serial sectioning revealed space formation at the interface,potentially caused by the volume shrinkage associated with the MgB_(2)formation or the combined effect of the volume shrinkage and the different thermal expansion coefficients of the MgB_(2)bulk,the filament,the mold,and the sealing material.These findings are expected to be pivotal in developing MgB_(2)superconducting joining technology for MRI magnet applications through interface engineering.
基金Project supported by the National Natural Science Foundation of China(Nos.11932008 and 12272156)the Fundamental Research Funds for the Central Universities(No.lzujbky-2022-kb06)+1 种基金the Gansu Science and Technology ProgramLanzhou City’s Scientific Research Funding Subsidy to Lanzhou University of China。
文摘Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting applications.With respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic fields.Traditional numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally demanding.Herein,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake coils.This approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic scale.We then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic scale.The results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and efficient.The proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.
基金the Natural Science Foundation of Henan Province(Grant Nos.212300410388 and 212300410238)the Scientific Research Innovation Team of Xuchang University(Grant No.2022CXTD005)+2 种基金the National Scientific Research Project Cultivation Fund of Xuchang University(Grant No.2022GJPY001)the Key Research Project in Universities of Henan Province(Grant No.23B140010)the“316"Project Plan of Xuchang University.
文摘Non-Hermitian dissipation dynamics,capable of turning the conventionally detrimental decoherence effects to useful resources for state engineering,is highly attractive to quantum information processing.In this work,an effective scheme is developed for implementing fast population transfer with a superconducting qutrit via the non-Hermitian shortcut to adiabaticity(STA).We first deal with aΛ-configuration interaction between the qutrit and microwave drivings,in which the dephasing-assisted qubit state inversion requiring an overlarge dephasing rate is constructed non-adiabatically.After introducing a feasible ancillary driving that directly acts upon the qubit states,the target state transfer can be well realized but with an accessible qubit dephasing rate.Moreover,a high fidelity could be numerically obtained in the considered system.The strategy could provide a new route towards the non-Hermitian shortcut operations on superconducting quantum circuits.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0704300)the National Natural Science Foundation of China(Grant No.U1932217)the StartUp Fund of Nanjing University of Posts and Telecommunications(Grant Nos.NY219087 and NY220038)。
文摘High-pressure structural search was performed on the hydrogen-rich compound LuBeH8at pressures up to 200 GPa.We found an Fm3m structure that exhibits stability and superconductivity above 100 GPa.Our phonon dispersion,electronic band structure,and superconductivity analyses in the 100–200 GPa pressure range reveal a strong electron–phonon coupling in Lu Be H8,while the superconducting critical temperature Tcshows a decreasing trend as the pressure increases,with T_(c)=255 K at 200 GPa and maximal T_(c)=355 K at 100 GPa.This study demonstrated the room-temperature superconductivity in Fm3m thus enriching the family of ternary hydrides.These findings provide valuable guidance for identifying new high-temperature superconducting hydrides.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104127 and 22131006)the Doctoral Starting Up Foundation of Hebei Normal University for Nationalities(Grant No.DR2020001)+1 种基金the Clean Energy(Carbon Peaking and Carbon Neutrality)Industry Research Institute of Chengde(Grant No.202205B090)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QA060)。
文摘On the basis of the current theoretical understanding of boron-based hard superconductors under ambient conditions,numerous studies have been conducted with the aim of developing superconducting materials with favorable mechanical properties using boron-rich compounds.In this paper,first-principles calculations reveal the existence of an unprecedented family of tetragonal pentaborides MB_(5)(M=Na,K,Rb,Ca,Sr,Ba,Sc,and Y),comprising B_(20)cages and centered metal atoms acting as stabilizers and electron donors to the boron sublattice.These compounds exhibit both superconductivity and high hardness,with the maximum superconducting transition temperature T_(c)of 18.6 K being achieved in RbB5 and the peak Vickers hardness Hv of 35.1 GPa being achieved in KB_(5)at 1 atm.The combination of these properties is particularly evident in KB_(5),RbB5,and BaB5,with Tc values of∼14.7,18.6,and 16.3 K and H_(v)values of∼35.1,32.4,and 33.8 GPa,respectively.The results presented here reveal that pentaborides can provide a framework for exploring and designing novel superconducting materials with favorable hardness at achievable pressures and even under ambient conditions.
基金Project supported by the National Natural Science Foundation of China(Nos.U2241267,1217215511872195)。
文摘Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers with its outstanding current-carrying capacity and mechanical properties.The REBCO tapes are wound spirally on the surface of CORC cable.Under extreme loadings,the REBCO tapes with layered composite structures are vulnerable,which can lead to degradation of critical current and even quenching of superconducting devices.In this paper,we simulate the deformation of CORC cable under external loads,and analyze the damage inside the tape with the cohesive zone model(CZM).Firstly,the fabrication and cabling of CORC are simulated,and the stresses and strains generated in the tape are extracted as the initial condition of the next step.Then,the tension and bending loads are applied to CORC cable,and the damage distribution inside the tape is presented.In addition,the effects of some parameters on the damage are discussed during the bending simulations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12274168 and 12074141)。
文摘An ultrafast pump-probe spectroscopy system combined with a cryogenic diamond anvil cell(DAC) instrument is developed to investigate the photo-excitation dynamic properties of condensed materials under low temperature and high pressure(LTHP) conditions.The ultrafast dynamics study is performed on Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi-2212) thin film under LTHP conditions.The superconducting(SC) phase transition has been observed by analyzing the ultrafast dynamics of Bi-2212 as a function of pressure and temperature.Our results suggest that the pump-probe spectroscopy system combined with a cryogenic DAC instrument is an effective method to study the physical mechanism of condensed matter physics at extreme conditions,especially for the SC phase transition.
基金the National Key Research and Development Program of China(Grant No.2021YFB3601201)the National Natural Science Foundation of China(Grant No.62101057)the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications)(Grant No.IPOC2021ZT07).
文摘Photonic crystal structures have excellent optical properties,so they are widely studied in conventional optical materials.Recent research shows that high-temperature superconducting periodic structures have natural photonic crystal features and they are favourable candidates for single-photon detection.Considering that superconductors have completely different properties from conventional optical materials,we study the energy level diagram and mid-infrared 3μm–5μm transmission spectrum of two-dimensional superconducting photonic crystals in both superconducting and quenched states with the finite element method.The energy level diagram of the circular crystal column superconducting structure shows that the structure has a large band gap width in both states.At the same fill factor,the circular crystal column superconducting structure has a larger band gap width than the others structures.For lattice structures,the zero transmission point of the square lattice structure is robust to the incident angle and environmental temperature.Our research has guiding significance for the design of new material photonic crystals,photon modulation and detection.
基金the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2018B030326001)the National Natural Science Foundation of China(Grant No.11874063),the National Natural Science Foundation of China(Grant No.11890704)+3 种基金the National Natural Science Foundation of China(Grant Nos.11934018 and T2121001)the Natural Science Foundation of Beijing(Grant No.Z190012)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)Beijing Natural Science Foundation(Grant No.Z200009)。
文摘The precise control and manipulation of the qubit state are vital for quantum simulation and quantum computation.In superconducting circuits,one notorious error comes from the crosstalk of microwave signals applied to different qubit control lines.In this work,we present a method for the calibration and cancellation of the microwave crosstalk and experimentally demonstrate its effectiveness in a superconducting 10-qubit chain.The method is convenient and efficient especially for calibrating the microwave crosstalk with large amplitudes and variations,which can be performed successively to reduce the microwave crosstalk by two to three orders.The qubit chain with microwave driving is governed by one-dimensional(1D)Bose-Hubbard model in transverse field,which is nonintegrable and shows thermalization behaviour during the time evolution from certain initial states.Such thermalization process is observed with excellent agreement between experiment and theory further confirming the effective global cancellation of the microwave crosstalk.
基金Project supported by the Key R&D Program of Guangdong Province,China(Grant No.2018B030326001)the National Natural Science Foundation of China(Grant Nos.11474152,12074179,U21A20436,and 61521001)the Natural Science Foundation of Jiangsu Province,China(Grant No.BE2021015-1)。
文摘Quantum many-body systems in which time-reversal symmetry is broken give rise to a wealth of exotic phases,and thus constitute one of the frontiers of modern condensed matter physics.Quantum simulation allows us to better understand many-body systems with huge Hilbert space,where classical simulation is usually inefficient.With superconducting quantum circuit as a platform for quantum simulation,we realize synthetic Abelian gauge fields by using microwave drive and tunable coupling in loop configurations to break the time-reversal symmetry of the system.Based on high-precision manipulation and readout of circuit-QED architecture,we demonstrate the chiral ground spin current of a time-reversal symmetry broken system with nontrivial interactions.Our work is a significant attempt to simulate quantum many-body systems with time-reversal symmetry breaking in multi-qubit superconducting processors.
基金the National Natural Science Foundation of China(Nos.11932008 and 11672120)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-kb01)。
文摘A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.
文摘The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this system are investigated using the two-band Ginzburg-Landau theory.We calculate the temperature dependence of upper critical field in arbitrary direction and critical supercurrent density through the FeSe film.It is revealed that the normalized upper critical field is independent of the film thickness and all of our theoretical results are in accordance with the experimental data.These thus strongly indicate the existence of two-gap s-wave superconductivity in this material.
基金financial supports from the Fund of Science and Technology on Reactor Fuel and Materials Laboratory(JCKYS2019201074)the Affiliated Hospital of Putian University,the Shenzhen Fundamental Research Program(JCYJ20220531095404009)+1 种基金the Shenzhen Knowledge Innovation Plan-Fundamental Research(Discipline Distribution)(JCYJ20180507184623297)the Major Science and Technology Infrastructure Project of Material Genome Big-science Facilities Platform supported by Municipal Development and Reform Commission of Shenzhen。
文摘Discovering new superconductors via traditional trial-and-error experimental approaches is apparently a time-consuming process,and the correlations between the critical temperature(Tc) and material features are still obscure.The rise of machine learning(ML) technology provides new opportunities to speed up inefficient exploration processes,and could potentially uncover new hints on the unclear correlations.In this work,we utilize open-source materials data,ML models,and data mining methods to explore the correlation between the chemical features and Tcvalues of superconducting materials.To further improve the prediction accuracy,a new model is created by integrating three basic algorithms,showing an enhanced accuracy with the coefficient of determination(R2) score of 95.9 % and root mean square error(RMSE) of 6.3 K.The average marginal contributions of material features towards Tcvalues are estimated to determine the importance of various features during prediction processes.The results suggest that the range thermal conductivity plays a critical role in Tcprediction among all element features.Furthermore,the integrated ML model is utilized to screen out potential twenty superconducting materials with Tcvalues beyond 50.0 K.This study provides insights towards Tcprediction to accelerate the exploration of potential high-Tcsuperconductors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12034018 and 11625419)。
文摘In quantum computation and quantum information processing, the manipulation and engineering of quantum systems to suit certain purposes are an ongoing task. One such example is quantum state transfer(QST), an essential requirement for both quantum communication and large-scale quantum computation. Here we engineer a chain of four superconducting qubits with tunable couplers to realize the perfect state transfer(PST) protocol originally proposed in quantum spin networks and successfully demonstrate the efficient transfer of an arbitrary single-qubit state from one end of the chain to the other,achieving a high fidelity of 0.986 in just 25 ns. This demonstrated QST is readily to extend to larger chain and multi-node configurations, thus serving as a desirable tool for scalable quantum information processing.
基金the Department of Science and Technology,Government of Gujarat for providing the necessary funds for the study。
文摘In this paper,we present observations of free oscillations of the Earth after major earthquakes in Chile(February 27,2010,Mw8.8)and Japan(March 11,2011,Mw9.1)using data from the dual-sphere superconducting gravimeter(SG-055),installed at Badargadh(23°0.47 N,70°0.62 E),Kutch,Gujarat,India in March 2009.To see the noise characteristics,we calculated the power spectral density of the gravity time series of 5 quiet days in the frequency band 0.05-20 mHz using the new low noise model(NLNM)as a reference.We compared the noise level of the Badargadh site to other SG sites around the world.This shows that the Badargadh SG is in a low noise state.We find that the noise increases at frequencies below 1 mHz.Such a characteristic is also observed in Djougou(Afrique,Benin)and Strasbourg(France).Using theoretical tides for Gujarat,we estimated a scale factor of about-814 nm/s~2/V for Gravl(lowersphere)and about-775 nm/s~2/V for Grav2(upper-sphere).We corrected the influence of atmospheric pressure from the one-second gravity data before switching to the frequency domain.We extracted a total of 53 Earth’s Free Oscillations(EFO)modes during the earthquake in Japan and about 47 EFO modes during the earthquake in Chile.We are able to extract the lowest0S2spheroidal mode(0.30945 mHz or54 min)and0S0radial mode(0.81439 mHz or 20 min).The longer time series shows individual0S2singlets and0S3(0.46855 mHz)singlets due to the Coriolis splitting effect.We cross-referenced the frequencies of these modes using the PREM model and previous global observations.The correlation coefficient between the observed and the PREM model for these two events are 0.999 for Japan earthquake and 0.993 for Chile earthquake.This validates the quality of the data useful for low-frequency studies in seismology.We also calculated the relative deviations of our observed fundamental modes with previously determined observed and theoretical values.We found that the relative deviations of our observed free oscillations do not exceed 0.5%,indicating good correlations.
基金Project supported by the Key-Area Research and Development Program of Guangdong Province of China (Grant No. 2018B030326001)the National Natural Science Foundation of China (Grant No. 11874065)+2 种基金the Guangdong Provincial Key Laboratory (Grant No. 2019B121203002)the Science, Technology and Innovation Commission of Shenzhen Municipality (Grant No. KYTDPT20181011104202253)the Shenzhen Hong Kong Cooperation Zone for Technology and Innovation of China (Grant No. HZQB-KCZYB2020050)。
文摘Quantum entanglement, a key resource in quantum information processing, is reduced by interaction between the quantum system concerned and its unavoidable noisy environment. Therefore it is of particular importance to study the dynamical properties of entanglement in open quantum systems. In this work, we mainly focus on two qubits coupled to an adjustable environment, namely a semi-infinite transmission line. The two qubits' relaxations, through individual channels or collective channel or both, can be adjusted by the qubits' transition frequencies. We examine entanglement dynamics in this model system with initial Werner state, and show that the phenomena of entanglement sudden death and revival can be observed. Due to the hardness of preparing the Werner state experimentally, we introduce a new type of entangled state called pseudo-Werner state, which preserves as much entangling property as the Werner state, and more importantly,it is experiment friendly. Furthermore, we provide detailed procedures for generating pseudo-Werner state and studying entanglement dynamics with it, which can be straightforwardly implemented in a superconducting waveguide quantum electrodynamics system.
基金supported by the CAS“Light of West China”Program (No.29Y936020)National Natural Science Foundation of China (No.12105331)Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB34010102)。
文摘In this study,a phenomenological model of the radio frequency(RF)behavior of a superconducting cavity fundamental power coupler is proposed by analyzing the simulation results of a transient beam-loading process in an extremely overcoupled superconducting cavity.Using this phenomenological model,the calculation of the transient reflected power from a superconducting cavity under beam loading can be mathematically simplified to algebraic operations without solving the differential equation governing the transient beam-loading process,while maintaining the calculation accuracy.Moreover,this phenomenological model can facilitate an intuitive understanding of the significant surge in the time evolution of reflected power from a superconducting cavity in certain beam-loading processes.The validity of this phenomenological model was carefully examined in various beam-loading processes and cavity conditions,and the method based on this phenomenological model was utilized in the transient RF analysis of the superconducting cavity system of the CAFe Linac,achieving satisfactory results.