Carbon dots that exhibit near-infrared fluorescence(NIR CDs)are considered emerging nanomaterials for advanced biomedical applications with low toxicity and superior photostability and targeting compared to currently ...Carbon dots that exhibit near-infrared fluorescence(NIR CDs)are considered emerging nanomaterials for advanced biomedical applications with low toxicity and superior photostability and targeting compared to currently used photoluminescence agents.Despite progress in the synthesis of NIR CDs,there remains a key obstacle to using them as an in vivo theranostic agent.This work demonstrates that the newly developed sulfur and nitrogen codoped NIR CDs are highly efficient in photothermal therapy(PTT)in mouse models(conversion efficiency of 59%)and can be readily visualized by photoluminescence and photoacoustic imaging.The real theranostic potential of NIR CDs is enhanced by their unique biodistribution and targeting.Contrary to all other nanomaterials that have been tested in biomedicine,they are excreted through the body’s renal filtration system.Moreover,after intravenous injection,NIR CDs are accumulated in tumor tissue via passive targeting,without any active species such as antibodies.Due to their accumulation in tumor tissue without the need for intratumor injection,high photothermal conversion,excellent optical and photoacoustic imaging performance,and renal excretion,the developed CDs are suitable for transfer to clinical biomedical practice.展开更多
In response to variable environmental conditions, guard cells located in the leaf epidermis can integrate and cope with a multitude of complicated stimuli, thereby making stomata in an appro- priate state. However, ma...In response to variable environmental conditions, guard cells located in the leaf epidermis can integrate and cope with a multitude of complicated stimuli, thereby making stomata in an appro- priate state. However, many signaling components in guard cell signaling remain elusive. In our laboratory, a tool for non-invasive remote infrared thermal images was used to screen an ethyl methane sulfonate-mutagenized population for Arabidopsis stomatal response mutants under multiple stresses (ABA, H2O2, CO2, etc.). More than forty "hot" or "cold" mutants were isolated (above or below 0.5℃ in con- trast to normal plantlets). Identification and primary genetic analysis of these mutants show that they are monogenic recessive mutations and there exist distinct difference in stomata apertures compared to wild type. These mutants in response to various environmental stresses and hormones were comprehen- sively investigated, which enables us to further un- derstand the cross-talk in different signal transduction pathways.展开更多
Mitogen-activated protein (MAP) kinase is involved in ABA- or H2O2-signaling, and H2O2 acts as inter-mediate in the downstream of ABA signal transduction pathway, which has recently emerged as a secondary mes-senger o...Mitogen-activated protein (MAP) kinase is involved in ABA- or H2O2-signaling, and H2O2 acts as inter-mediate in the downstream of ABA signal transduction pathway, which has recently emerged as a secondary mes-senger of ABA signaling. Using an epidermal strip bioassay and laser scanning confocal microscope, we provided the first evidence that MAP kinase plays an important role in H2O2 signal initial, amplification and specific targeting in response to stimuli in guard cells. ABA- or H2O2-induced Vicia faba stomatal closure was inhibited or reversed by the specific inhibitor PD98059 of MEK1/2; the guard cells were pre-incubated or -microinjected by 10 mmol·L-1 PD98059, ABA could not enhance the fluorescence intensity of H2O2 probe dichlorofluorescein (DCF). Meanwhile, after ABA induced the H2O2 accumulation in guard cells, the exogenous or intracellular PD98059 could reduce the DCF fluorescence intensity. Most interestingly, on the contrary to ABA, the DCF fluorescence intensity of guard cells treated by 100 mmol·L-1 salicylic acid (SA) was not down-regulated by PD98059, yet PD98059 did not regulate the stomatal move-ment being induced by light, dark or salicylic acid. These results suggest that MEK1/2 could mediate stomatal closure by abolishing the ABA-induced H2O2 generation/accumula- tion in the specific manner.展开更多
Reactive oxygen species(ROS)are produced as undesirable by-products of metabolism in various cellular compartments,especially in response to unfavorable environmental conditions,throughout the life cycle of plants.Str...Reactive oxygen species(ROS)are produced as undesirable by-products of metabolism in various cellular compartments,especially in response to unfavorable environmental conditions,throughout the life cycle of plants.Stressinduced ROS production disrupts normal cellular function and leads to oxidative damage.To cope with excessive ROS,plants are equipped with a sophisticated antioxidative defense system consisting of enzymatic and non-enzymatic components that scavenge ROS or inhibit their harmful effects on biomolecules.Nonetheless,when maintained at relatively low levels,ROS act as signaling molecules that regulate plant growth,development,and adaptation to adverse conditions.Here,we provide an overview of current approaches for detecting ROS.We also discuss recent advances in understanding ROS signaling,ROS metabolism,and the roles of ROS in plant growth and responses to various abiotic stresses.展开更多
The phytohormone abscisic acid (ABA) plays a critical role in plant growth, development, and adaptation to various stress conditions. The cellular ABA level is constantly adjusted to respond to changing physiological ...The phytohormone abscisic acid (ABA) plays a critical role in plant growth, development, and adaptation to various stress conditions. The cellular ABA level is constantly adjusted to respond to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning ABA levels remain elusive. Here, we report that BGLU10, a member of a multigene family of β-glucosidases, contributes to drought tolerance in Arabidopsis. The T-DNA insertion mutant bglu10 exhibited a droughtsensitive phenotype, characterized by an increased rate of water loss, and lower leaf temperature, β-glucosidase activity, ABA content, and expressions of ABA-and drought-responsive genes under drought stress. In contrast, lines overexpressing BGLU10 showed greater drought resistance than that of the wild-type, as shown by decreased water loss via transpiration, higher β-glucosidase activity, ABA level, and expressions of ABA- and stress-responsive genes under drought stress. Transient expression of BGLU10::GFP and γ-TIP1::RFP in mesophyll cell protoplasts showed that the BGLU10 enzyme protein was localized to the vacuole. Meanwhile, BGLU10 was expressed in various organs, and was induced by several abiotic stresses, suggesting that BGLU10 may be involved in a variety of stress responses, and that hydrolysis of ABA-GE produces free ABA in the plant stress response.展开更多
Gibberellin(GA)functions in plant growth and development.However,genes involved in the biosynthesis and regulation of GA in crop plants are poorly understood.We isolated the mutant gad5-1(GAAssociated Dwarf 5),charact...Gibberellin(GA)functions in plant growth and development.However,genes involved in the biosynthesis and regulation of GA in crop plants are poorly understood.We isolated the mutant gad5-1(GAAssociated Dwarf 5),characterized by dwarfing,short internodes,and dark green and short leaves.Map-based gene cloning and allelic verification confirmed that ZmGAD5 encodes ent-kaurenoic acid oxidase(KAO),which catalyzes KA(ent-kaurenoic acid)to GA12 conversion during GA biosynthesis in maize.ZmGAD5 is localized to the endoplasmic reticulum and is present in multiple maize organs.In gad5-1,the expression of ZmGAD5 is severely reduced,and the levels of the direct substrate of KAO,KA,is increased,leading to a reduction in GA content.The abnormal phenotype of gad5-1 was restored by exogenous application of GA3.The biomass,plant height,and levels of GA12 and GA3 in transgenic Arabidopsis overexpressing ZmGAD5 were increased in comparison with the corresponding controls Col-0.These findings deepen our understanding of genes involved in GA biosynthesis,and could lead to the development of maize lines with improved architecture and higher planting-density tolerance.展开更多
Quantum computation (QC) offers the promise of enhanced computational capabilities and drastic accelerations in solving complex tasks such as quantum chemistry^([1,2])and prime factorization.^([3])Various physical imp...Quantum computation (QC) offers the promise of enhanced computational capabilities and drastic accelerations in solving complex tasks such as quantum chemistry^([1,2])and prime factorization.^([3])Various physical implementations for practical QC are being pursued across the academic and industrial research initiatives.Exemplary ones include trapped ions,^([4])nuclear spin,^([5]).展开更多
The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully disc...The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully discrete DLM/FD-mixed finite element scheme are developed for the first time for this problem with a moving interface,where the arbitrary Lagrangian-Eulerian(ALE)technique is employed to deal with the moving and immersed subdomain.Stability and optimal convergence properties are obtained for both schemes.Numerical experiments are carried out for different scenarios of jump coefficients,and all theoretical results are validated.展开更多
Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two...Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two resonant modes of the Hamiltonian become degenerate.Near the EP,the system could be more sensitive to external perturbations and this may lead to enhanced sensing.In this paper,we present experimental results on the observation of PT symmetry broken transition and the EP using a tunable superconducting qubit.The quantum system of investigation is formed by the two levels of the qubit and the energy loss of the system to the environment is controlled by a method of parametric modulation of the qubit frequency.This method is simple with no requirements for additional elements or qubit device modifications.We believe it can be easily implemented on multi-qubit devices that would be suitable for further exploration of non-Hermitian physics in more complex and diverse systems.展开更多
We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artifi...We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler-Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.展开更多
Josephson parameter amplifier(JPA)is a microwave signal amplifier device with near-quantum-limit-noise performance.It has important applications in scientific research fields such as quantum computing and dark matter ...Josephson parameter amplifier(JPA)is a microwave signal amplifier device with near-quantum-limit-noise performance.It has important applications in scientific research fields such as quantum computing and dark matter detection.This work reports the fabrication and characterization of broadband JPA devices and their applications in multi-qubit readout and squeezing of vacuum state.We use a process in which transmission lines and electrodes are made of niobium thin film and aluminum Josephson junctions are made by Dolan bridge technique.We believe this process is more convenient than the process we used previously.The whole production process adopts electron beam lithography technology to ensure high structural resolution.The test result shows that the gain value of the manufactured JPA can exceed 15 dB,and the amplification bandwidth is about 400 MHz.The noise temperature is about 400 mK at the working frequency of 6.2 GHz.The devices have been successfully used in experiments involving superconducting multi-qubit quantum processors.Furthermore,the device is applied to squeeze vacuum fluctuations and a squeezing level of 1.635 dB is achieved.展开更多
We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper crit...We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper critical field(Hc2)in parallel to surface orientation shows bending curvature close to critical temperature Tc,suggesting a two-dimensional(2D)nature of the samples.The 2D behavior is further supported by the angular dependence measurements of Hc2 for the thinnest samples.The temperature dependence of parallel upper critical field for the thick films could be described by a model based on the anisotropic Ginzburg-Landau theory.Interestingly,the results measured in the field perpendicular to the film surface orientation show a similar bending curvature but in a much narrow temperature region close to Tc for the ultra-thin samples.We suggest that this feature could be due to suppression of pair-breaking caused by local in-homogeneity.We further propose the temperature dependence of perpendicular Hc2 as a measure of uniformity of superconducting ultra-thin films.For the thick samples,we find that Hc2 shows maxima for both parallel and perpendicular orientations.The Hc2 peak for the perpendicular orientation is believed to be due to the columnar structure formed during the growth of the thick films.The presence of columnar structure is confirmed by transmission electron microscopy(TEM).In addition,we have measured the angular dependence of magneto-resistance,and the results are consistent with the Hc2 data.展开更多
基金supported by the National Natural Science Foundation of China(Project nos.51602304,91739117,81527024,61335001,and 81771930)the Youth Innovation Promotion Association of CAS+2 种基金the Jilin Province Science and Technology Research(Project nos.20170101191JC,20170101042JC,20160520008JH,and 20150519003JH)the Shenzhen Science and Technology Innovation Commission(Grant no.JCYJ20170307110157501)the support by the Operational Proqramme Research,Development and Education-European Reqional Development Fund,Project No.CZ.02.1.01/0.0/0.0/16-019/0000754 of the Ministry of Education,Youth and Sports of the Czech Republic and the assistance provided by the Research Infrastructure NanoEnviCz supported by the Ministry of Education,Youth and Sports of the Czech Republic under Project L01305 of the Ministry of Education,Youth and Sports of the Czech Republic.
文摘Carbon dots that exhibit near-infrared fluorescence(NIR CDs)are considered emerging nanomaterials for advanced biomedical applications with low toxicity and superior photostability and targeting compared to currently used photoluminescence agents.Despite progress in the synthesis of NIR CDs,there remains a key obstacle to using them as an in vivo theranostic agent.This work demonstrates that the newly developed sulfur and nitrogen codoped NIR CDs are highly efficient in photothermal therapy(PTT)in mouse models(conversion efficiency of 59%)and can be readily visualized by photoluminescence and photoacoustic imaging.The real theranostic potential of NIR CDs is enhanced by their unique biodistribution and targeting.Contrary to all other nanomaterials that have been tested in biomedicine,they are excreted through the body’s renal filtration system.Moreover,after intravenous injection,NIR CDs are accumulated in tumor tissue via passive targeting,without any active species such as antibodies.Due to their accumulation in tumor tissue without the need for intratumor injection,high photothermal conversion,excellent optical and photoacoustic imaging performance,and renal excretion,the developed CDs are suitable for transfer to clinical biomedical practice.
基金This work was supported by the National Key Basic Special Funds(Grant No.2003CB114305)the National Natural Science Foundation of China(Grant Nos.39870372,30370765 and 30440079).
文摘In response to variable environmental conditions, guard cells located in the leaf epidermis can integrate and cope with a multitude of complicated stimuli, thereby making stomata in an appro- priate state. However, many signaling components in guard cell signaling remain elusive. In our laboratory, a tool for non-invasive remote infrared thermal images was used to screen an ethyl methane sulfonate-mutagenized population for Arabidopsis stomatal response mutants under multiple stresses (ABA, H2O2, CO2, etc.). More than forty "hot" or "cold" mutants were isolated (above or below 0.5℃ in con- trast to normal plantlets). Identification and primary genetic analysis of these mutants show that they are monogenic recessive mutations and there exist distinct difference in stomata apertures compared to wild type. These mutants in response to various environmental stresses and hormones were comprehen- sively investigated, which enables us to further un- derstand the cross-talk in different signal transduction pathways.
文摘Mitogen-activated protein (MAP) kinase is involved in ABA- or H2O2-signaling, and H2O2 acts as inter-mediate in the downstream of ABA signal transduction pathway, which has recently emerged as a secondary mes-senger of ABA signaling. Using an epidermal strip bioassay and laser scanning confocal microscope, we provided the first evidence that MAP kinase plays an important role in H2O2 signal initial, amplification and specific targeting in response to stimuli in guard cells. ABA- or H2O2-induced Vicia faba stomatal closure was inhibited or reversed by the specific inhibitor PD98059 of MEK1/2; the guard cells were pre-incubated or -microinjected by 10 mmol·L-1 PD98059, ABA could not enhance the fluorescence intensity of H2O2 probe dichlorofluorescein (DCF). Meanwhile, after ABA induced the H2O2 accumulation in guard cells, the exogenous or intracellular PD98059 could reduce the DCF fluorescence intensity. Most interestingly, on the contrary to ABA, the DCF fluorescence intensity of guard cells treated by 100 mmol·L-1 salicylic acid (SA) was not down-regulated by PD98059, yet PD98059 did not regulate the stomatal move-ment being induced by light, dark or salicylic acid. These results suggest that MEK1/2 could mediate stomatal closure by abolishing the ABA-induced H2O2 generation/accumula- tion in the specific manner.
基金supported by the National Natural Science Foundation of China(U21A20206,32322010)the Program for Innovative Research Team(in Science and Technology)at the University of Henan Province(21IRTSTHN019)。
文摘Reactive oxygen species(ROS)are produced as undesirable by-products of metabolism in various cellular compartments,especially in response to unfavorable environmental conditions,throughout the life cycle of plants.Stressinduced ROS production disrupts normal cellular function and leads to oxidative damage.To cope with excessive ROS,plants are equipped with a sophisticated antioxidative defense system consisting of enzymatic and non-enzymatic components that scavenge ROS or inhibit their harmful effects on biomolecules.Nonetheless,when maintained at relatively low levels,ROS act as signaling molecules that regulate plant growth,development,and adaptation to adverse conditions.Here,we provide an overview of current approaches for detecting ROS.We also discuss recent advances in understanding ROS signaling,ROS metabolism,and the roles of ROS in plant growth and responses to various abiotic stresses.
基金supported by the National Natural Science Foundation of China (90817106, 31170253 and 30800075)
文摘The phytohormone abscisic acid (ABA) plays a critical role in plant growth, development, and adaptation to various stress conditions. The cellular ABA level is constantly adjusted to respond to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning ABA levels remain elusive. Here, we report that BGLU10, a member of a multigene family of β-glucosidases, contributes to drought tolerance in Arabidopsis. The T-DNA insertion mutant bglu10 exhibited a droughtsensitive phenotype, characterized by an increased rate of water loss, and lower leaf temperature, β-glucosidase activity, ABA content, and expressions of ABA-and drought-responsive genes under drought stress. In contrast, lines overexpressing BGLU10 showed greater drought resistance than that of the wild-type, as shown by decreased water loss via transpiration, higher β-glucosidase activity, ABA level, and expressions of ABA- and stress-responsive genes under drought stress. Transient expression of BGLU10::GFP and γ-TIP1::RFP in mesophyll cell protoplasts showed that the BGLU10 enzyme protein was localized to the vacuole. Meanwhile, BGLU10 was expressed in various organs, and was induced by several abiotic stresses, suggesting that BGLU10 may be involved in a variety of stress responses, and that hydrolysis of ABA-GE produces free ABA in the plant stress response.
基金the National Natural Science Foundation of China(U21A20206,Chun-Peng Song)the Project of Sanya Yazhou Bay Science and Technology City(SCKJJYRC-2022-78,Baozhu Li)+1 种基金the Program for Innovative Research Team(in Science and Technology)in University of Henan Province(21IRTSTHN019,Siyi Guo)the 111 Project of China(D16014).
文摘Gibberellin(GA)functions in plant growth and development.However,genes involved in the biosynthesis and regulation of GA in crop plants are poorly understood.We isolated the mutant gad5-1(GAAssociated Dwarf 5),characterized by dwarfing,short internodes,and dark green and short leaves.Map-based gene cloning and allelic verification confirmed that ZmGAD5 encodes ent-kaurenoic acid oxidase(KAO),which catalyzes KA(ent-kaurenoic acid)to GA12 conversion during GA biosynthesis in maize.ZmGAD5 is localized to the endoplasmic reticulum and is present in multiple maize organs.In gad5-1,the expression of ZmGAD5 is severely reduced,and the levels of the direct substrate of KAO,KA,is increased,leading to a reduction in GA content.The abnormal phenotype of gad5-1 was restored by exogenous application of GA3.The biomass,plant height,and levels of GA12 and GA3 in transgenic Arabidopsis overexpressing ZmGAD5 were increased in comparison with the corresponding controls Col-0.These findings deepen our understanding of genes involved in GA biosynthesis,and could lead to the development of maize lines with improved architecture and higher planting-density tolerance.
文摘Quantum computation (QC) offers the promise of enhanced computational capabilities and drastic accelerations in solving complex tasks such as quantum chemistry^([1,2])and prime factorization.^([3])Various physical implementations for practical QC are being pursued across the academic and industrial research initiatives.Exemplary ones include trapped ions,^([4])nuclear spin,^([5]).
基金P.Sun was supported by NSF Grant DMS-1418806C.S.Zhang was partially supported by the National Key Research and Development Program of China(Grant No.2016YFB0201304)+1 种基金the Major Research Plan of National Natural Science Foundation of China(Grant Nos.91430215,91530323)the Key Research Program of Frontier Sciences of CAS.
文摘The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully discrete DLM/FD-mixed finite element scheme are developed for the first time for this problem with a moving interface,where the arbitrary Lagrangian-Eulerian(ALE)technique is employed to deal with the moving and immersed subdomain.Stability and optimal convergence properties are obtained for both schemes.Numerical experiments are carried out for different scenarios of jump coefficients,and all theoretical results are validated.
基金supported by the State Key Development Program for Basic Research of China(Grant Nos.2017YFA0304300 and 2016YFA0300600)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303030001)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000).
文摘Open physical systems described by the non-Hermitian Hamiltonian with parity-time-reversal(PT)symmetry show peculiar phenomena,such as the presence of an exceptional point(EP)at which the PT symmetry is broken and two resonant modes of the Hamiltonian become degenerate.Near the EP,the system could be more sensitive to external perturbations and this may lead to enhanced sensing.In this paper,we present experimental results on the observation of PT symmetry broken transition and the EP using a tunable superconducting qubit.The quantum system of investigation is formed by the two levels of the qubit and the energy loss of the system to the environment is controlled by a method of parametric modulation of the qubit frequency.This method is simple with no requirements for additional elements or qubit device modifications.We believe it can be easily implemented on multi-qubit devices that would be suitable for further exploration of non-Hermitian physics in more complex and diverse systems.
基金Project supported by the Science Funds from the Ministry of Science and Technology of China(Grant Nos.2014CB921401,2017YFA0304300,2014CB921202,and 2016YFA0300601)the National Natural Science Foundation of China(Grant No.11674376)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07010300)
文摘We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler-Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.
基金Project supported by the State Key Development Program for Basic Research of China(Grant No.2017YFA0304300)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303030001)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)。
文摘Josephson parameter amplifier(JPA)is a microwave signal amplifier device with near-quantum-limit-noise performance.It has important applications in scientific research fields such as quantum computing and dark matter detection.This work reports the fabrication and characterization of broadband JPA devices and their applications in multi-qubit readout and squeezing of vacuum state.We use a process in which transmission lines and electrodes are made of niobium thin film and aluminum Josephson junctions are made by Dolan bridge technique.We believe this process is more convenient than the process we used previously.The whole production process adopts electron beam lithography technology to ensure high structural resolution.The test result shows that the gain value of the manufactured JPA can exceed 15 dB,and the amplification bandwidth is about 400 MHz.The noise temperature is about 400 mK at the working frequency of 6.2 GHz.The devices have been successfully used in experiments involving superconducting multi-qubit quantum processors.Furthermore,the device is applied to squeeze vacuum fluctuations and a squeezing level of 1.635 dB is achieved.
基金the Chinese Academy of Sciences(Grant No.XDB25000000).
文摘We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper critical field(Hc2)in parallel to surface orientation shows bending curvature close to critical temperature Tc,suggesting a two-dimensional(2D)nature of the samples.The 2D behavior is further supported by the angular dependence measurements of Hc2 for the thinnest samples.The temperature dependence of parallel upper critical field for the thick films could be described by a model based on the anisotropic Ginzburg-Landau theory.Interestingly,the results measured in the field perpendicular to the film surface orientation show a similar bending curvature but in a much narrow temperature region close to Tc for the ultra-thin samples.We suggest that this feature could be due to suppression of pair-breaking caused by local in-homogeneity.We further propose the temperature dependence of perpendicular Hc2 as a measure of uniformity of superconducting ultra-thin films.For the thick samples,we find that Hc2 shows maxima for both parallel and perpendicular orientations.The Hc2 peak for the perpendicular orientation is believed to be due to the columnar structure formed during the growth of the thick films.The presence of columnar structure is confirmed by transmission electron microscopy(TEM).In addition,we have measured the angular dependence of magneto-resistance,and the results are consistent with the Hc2 data.
