Network virtualization can effectively establish dedicated virtual networks to implement various network functions.However,the existing research works have some shortcomings,for example,although computing resource pro...Network virtualization can effectively establish dedicated virtual networks to implement various network functions.However,the existing research works have some shortcomings,for example,although computing resource properties of individual nodes are considered,node storage properties and the network topology properties are usually ignored in Virtual Network(VN)modelling,which leads to the inaccurate measurement of node availability and priority.In addition,most static virtual network mapping methods allocate fixed resources to users during the entire life cycle,and the users’actual resource requirements vary with the workload,which results in resource allocation redundancy.Based on the above analysis,in this paper,we propose a dynamic resource sharing virtual network mapping algorithm named NMA-PRS-VNE,first,we construct a new,more realistic network framework in which the properties of nodes include computing resources,storage resources and topology properties.In the node mapping process,three properties of the node are used to measure its mapping ability.Second,we consider the resources of adjacent nodes and links instead of the traditional method of measuring the availability and priority of nodes by considering only the resource properties,so as to more accurately select the physical mapping nodes that meet the constraints and conditions and improve the success rate of subsequent link mapping.Finally,we divide the resource requirements of Virtual Network Requests(VNRs)into basic subrequirements and variable sub-variable requirements to complete dynamic resource allocation.The former represents monopolizing resource requirements by the VNRs,while the latter represents shared resources by many VNRs with the probability of occupying resources,where we keep a balance between resource sharing and collision among users by calculating the collision probability.Simulation results show that the proposed NMAPRS-VNE can increase the average acceptance rate and network revenue by 15%and 38%,and reduce the network cost and link pressure by 25%and 17%.展开更多
Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various c...Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various classical systems.Although a Hamiltonian with anti-PT symmetry only differs from its PT-symmetric counterpart in a global phase,the information and energy exchange between systems and environment are different under them.It is also suggested theoretically that anti-PT symmetry is a useful concept in the context of quantum information storage with qubits coupled to a bosonic bath.So far,the observation of anti-PT symmetry in individual quantum systems remains elusive.Here,we implement an anti-PT-symmetric Hamiltonian of a single qubit in a single trapped ion by a designed microwave and optical control-pulse sequence.We characterize the anti-PT phase transition by mapping out the eigenvalues at different ratios between coupling strengths and dissipation rates.The full information of the quantum state is also obtained by quantum state tomography.Our work allows quantum simulation of genuine open-system feature of an anti-PT-symmetric system,which paves the way for utilizing non-Hermitian properties for quantum information processing.展开更多
As a complementary analysis tool to conventional high-field nuclear magnetic resonance(NMR),zero-to ultralow-field(ZULF)NMR detects nuclear magnetization signals in the sub-microtesla regime.Spin-exchange relaxation-f...As a complementary analysis tool to conventional high-field nuclear magnetic resonance(NMR),zero-to ultralow-field(ZULF)NMR detects nuclear magnetization signals in the sub-microtesla regime.Spin-exchange relaxation-free(SERF)atomic magnetometers provide a new generation of sensitive detectors for ZULF NMR.Owing to features such as low cost,high resolution,and portability,ZULF NMR has recently attracted considerable attention in chemistry,biology,medicine,and tests of fundamental physics.This review describes the basic principles,methodology,and recent experimental and theoretical development of ZULF NMR as well as its applications in spectroscopy,quantum control,imaging,NMR-based quantum devices,and tests of fundamental physics.The future prospects of ZULF NMR are also discussed.展开更多
Quantum state transfer between two distant parties is at the heart of quantum computation and quantum communication.Among the various protocols,the counterdiabatic driving(CD)method,by suppressing the unwanted transit...Quantum state transfer between two distant parties is at the heart of quantum computation and quantum communication.Among the various protocols,the counterdiabatic driving(CD)method,by suppressing the unwanted transitions with an auxiliary Hamiltonian Hcd(t),offers a fast and robust strategy to transfer quantum states.However,Hcd(t)term often takes a complicated form in higherdimensional systems and is difficult to realize in experiment.Recently,the Floquet-engineered method was proposed to emulate the dynamics induced by Hcd(t)without the need for complex interactions in multi-qubit systems,which can accelerate the adiabatic process through the fast-oscillating control in the original Hamiltonian H0(t).Here,we apply this method in the Heisenberg spin chains,with only control of the two marginal couplings,to achieve the fast,high-fidelity,and robust quantum state transfer.Then we report an experimental implementation of our scheme using a nuclear magnetic resonance simulator.The experimental results demonstrate the feasibility of this method in complex many-body system and thus provide a new alternative to realize the high-fidelity quantum state manipulation in practice.展开更多
The enhanced patch test proposed by Chen W J(2006) can be used to assess the convergence of the problem with non-homogeneous differential equations.Based on this theory,we establish the patch test function for axisymm...The enhanced patch test proposed by Chen W J(2006) can be used to assess the convergence of the problem with non-homogeneous differential equations.Based on this theory,we establish the patch test function for axisymmetric elements of conventional and couple stress theories,and reach an important conclusion that the patch test function for axisymmetric elements cannot contain non-zero constant shear.展开更多
Solar driven CO_(2) conversion into high-value-added chemicals and energy-rich fuels is one of the promising strategies to tackle global warming and to address the energy-supply crisis.Even though enormous effort has ...Solar driven CO_(2) conversion into high-value-added chemicals and energy-rich fuels is one of the promising strategies to tackle global warming and to address the energy-supply crisis.Even though enormous effort has been devoted to exploring all sorts of homogeneous and heterogeneous photocatalysts,the current efficiency and more importantly selectivity to valuable chemicals are still rather moderate,thus it is desired to develop high-efficiency photocatalytic system toward CO_(2) reduction with excellent selectivity.In this review,fundamental aspects of photocatalytic CO_(2) reduction by pure water,the reaction systems and the reliable method for detection of the products are firstly described.Thereafter the recent advances of the main strategy for improving the photocatalytic CO_(2) reduction from the perspective of promoting the CO_(2) adsorption and activation,accelerating the kinetics of water oxidation,and modulating charge separation are overviewed.The prospects and challenges on precise designing heterogeneous catalysts for CO_(2) photoreduction are proposed at the end,indicating the significance for the further development of photocatalytic systems with high CO_(2) conversion efficiency and product selectivity.展开更多
基金We are grateful for the support of the Natural Science Foundation of Shandong Province(No.ZR2020LZH008,ZR2020QF112,ZR2019MF071)the National Natural Science Foundation of China(61373149).
文摘Network virtualization can effectively establish dedicated virtual networks to implement various network functions.However,the existing research works have some shortcomings,for example,although computing resource properties of individual nodes are considered,node storage properties and the network topology properties are usually ignored in Virtual Network(VN)modelling,which leads to the inaccurate measurement of node availability and priority.In addition,most static virtual network mapping methods allocate fixed resources to users during the entire life cycle,and the users’actual resource requirements vary with the workload,which results in resource allocation redundancy.Based on the above analysis,in this paper,we propose a dynamic resource sharing virtual network mapping algorithm named NMA-PRS-VNE,first,we construct a new,more realistic network framework in which the properties of nodes include computing resources,storage resources and topology properties.In the node mapping process,three properties of the node are used to measure its mapping ability.Second,we consider the resources of adjacent nodes and links instead of the traditional method of measuring the availability and priority of nodes by considering only the resource properties,so as to more accurately select the physical mapping nodes that meet the constraints and conditions and improve the success rate of subsequent link mapping.Finally,we divide the resource requirements of Virtual Network Requests(VNRs)into basic subrequirements and variable sub-variable requirements to complete dynamic resource allocation.The former represents monopolizing resource requirements by the VNRs,while the latter represents shared resources by many VNRs with the probability of occupying resources,where we keep a balance between resource sharing and collision among users by calculating the collision probability.Simulation results show that the proposed NMAPRS-VNE can increase the average acceptance rate and network revenue by 15%and 38%,and reduce the network cost and link pressure by 25%and 17%.
基金the Key-Area Research and Development Program of Guangdong Province(2019B030330001)the National Natural Science Foundation of China(11774436,11974434 and 12074439)+3 种基金the fundamental research funds for the Central Universities(Sun Yat-sen University,2021qntd28)Le Luo receives support from Guangdong Province Youth Talent Program(2017GC010656)Sun Yat-Sen University Core Technology Development Fund.Yang Liu receives support from Natural Science Foundation of Guangdong Province(2020A1515011159)Ji Bian receives support from China Postdoctoral Science Foundation(2021M703768).
文摘Non-Hermitian systems satisfying parity-time(PT)symmetry have aroused considerable interest owing to their exotic features.Anti-PT symmetry is an important counterpart of the symmetry,and has been studied in various classical systems.Although a Hamiltonian with anti-PT symmetry only differs from its PT-symmetric counterpart in a global phase,the information and energy exchange between systems and environment are different under them.It is also suggested theoretically that anti-PT symmetry is a useful concept in the context of quantum information storage with qubits coupled to a bosonic bath.So far,the observation of anti-PT symmetry in individual quantum systems remains elusive.Here,we implement an anti-PT-symmetric Hamiltonian of a single qubit in a single trapped ion by a designed microwave and optical control-pulse sequence.We characterize the anti-PT phase transition by mapping out the eigenvalues at different ratios between coupling strengths and dissipation rates.The full information of the quantum state is also obtained by quantum state tomography.Our work allows quantum simulation of genuine open-system feature of an anti-PT-symmetric system,which paves the way for utilizing non-Hermitian properties for quantum information processing.
基金This work was supported by National Key Research and Development Program of China(Grant no.2018YFA0306600)National Natural Science Foun-dation of China(Grants nos.11661161018,11927811)+1 种基金Anhui Initia-tive in Quantum Information Technologies(Grant No.AHY050000)USTC Research Funds of the Double First-Class Initiative(Grant no.YD3540002002).
文摘As a complementary analysis tool to conventional high-field nuclear magnetic resonance(NMR),zero-to ultralow-field(ZULF)NMR detects nuclear magnetization signals in the sub-microtesla regime.Spin-exchange relaxation-free(SERF)atomic magnetometers provide a new generation of sensitive detectors for ZULF NMR.Owing to features such as low cost,high resolution,and portability,ZULF NMR has recently attracted considerable attention in chemistry,biology,medicine,and tests of fundamental physics.This review describes the basic principles,methodology,and recent experimental and theoretical development of ZULF NMR as well as its applications in spectroscopy,quantum control,imaging,NMR-based quantum devices,and tests of fundamental physics.The future prospects of ZULF NMR are also discussed.
基金financially supported by the National Natural Science Foundation of China (11847016, 11425523 and 11661161018)National Key Research and Development Program of China (2018YFA0306600)Anhui Initiative in Quantum Information Technologies (AHY050000)
文摘Quantum state transfer between two distant parties is at the heart of quantum computation and quantum communication.Among the various protocols,the counterdiabatic driving(CD)method,by suppressing the unwanted transitions with an auxiliary Hamiltonian Hcd(t),offers a fast and robust strategy to transfer quantum states.However,Hcd(t)term often takes a complicated form in higherdimensional systems and is difficult to realize in experiment.Recently,the Floquet-engineered method was proposed to emulate the dynamics induced by Hcd(t)without the need for complex interactions in multi-qubit systems,which can accelerate the adiabatic process through the fast-oscillating control in the original Hamiltonian H0(t).Here,we apply this method in the Heisenberg spin chains,with only control of the two marginal couplings,to achieve the fast,high-fidelity,and robust quantum state transfer.Then we report an experimental implementation of our scheme using a nuclear magnetic resonance simulator.The experimental results demonstrate the feasibility of this method in complex many-body system and thus provide a new alternative to realize the high-fidelity quantum state manipulation in practice.
基金Supported by the National Natural Science Foundation of China (Grant No. 10672032)
文摘The enhanced patch test proposed by Chen W J(2006) can be used to assess the convergence of the problem with non-homogeneous differential equations.Based on this theory,we establish the patch test function for axisymmetric elements of conventional and couple stress theories,and reach an important conclusion that the patch test function for axisymmetric elements cannot contain non-zero constant shear.
基金National Natural Science Foundation of China(no.U1805255,U2102211)Royal Society Newton Advanced Fellowship grant(NAF\R1\191163),UK EPSR C(EP/S018204/2)+1 种基金Leverhulme Trust(RPG-2017-122)Royal Society Leverhulme Trust Senior Research Fellowship(SRF\R1\21000153).
文摘Solar driven CO_(2) conversion into high-value-added chemicals and energy-rich fuels is one of the promising strategies to tackle global warming and to address the energy-supply crisis.Even though enormous effort has been devoted to exploring all sorts of homogeneous and heterogeneous photocatalysts,the current efficiency and more importantly selectivity to valuable chemicals are still rather moderate,thus it is desired to develop high-efficiency photocatalytic system toward CO_(2) reduction with excellent selectivity.In this review,fundamental aspects of photocatalytic CO_(2) reduction by pure water,the reaction systems and the reliable method for detection of the products are firstly described.Thereafter the recent advances of the main strategy for improving the photocatalytic CO_(2) reduction from the perspective of promoting the CO_(2) adsorption and activation,accelerating the kinetics of water oxidation,and modulating charge separation are overviewed.The prospects and challenges on precise designing heterogeneous catalysts for CO_(2) photoreduction are proposed at the end,indicating the significance for the further development of photocatalytic systems with high CO_(2) conversion efficiency and product selectivity.
