Herein, we present an approach to look for the best phenomenon to measure quantum correlation. The system of two isolated qubits each interacting with a single-mode cavity was theoretically created to study the quantu...Herein, we present an approach to look for the best phenomenon to measure quantum correlation. The system of two isolated qubits each interacting with a single-mode cavity was theoretically created to study the quantum correlation. Some of the phenomena, such as the quantum discord and concurrence, were generated through such a system. The influences of initial state purity, qubit motion, and detuning parameters were discussed for the phenomena. These parameters for a specific value show that the behavior of phenomena are analogous. It is interesting to mention that some values of detuning undergo a sudden death of phenomena, and the quantum discord still captures the qubits quantum correlation. We predict that the quantum discord may be a better measure of quantum correlation than concurrence.展开更多
In this paper, we consider the interaction between two two-level atoms and a two-mode binomial field with a general intensity-dependent coupling regime. The outlined dynamical problem has explicit analytical solution,...In this paper, we consider the interaction between two two-level atoms and a two-mode binomial field with a general intensity-dependent coupling regime. The outlined dynamical problem has explicit analytical solution, by which we can evaluate a few of its physical features of interest. To achieve the purpose of the paper, after choosing a particular nonlinearity function, we investigate the quantum statistics, atomic population inversion and at last the linear entropy of the atom-field system which is a good measure for the degree of entanglement. In detail, the effects of binomial field parameters, in addition to different initial atomic states on the temporal behavior of the mentioned quantities have been analyzed. The results show that, the values of binomial field parameters and the initial state of the two atoms influence on the nonclassical effects in the obtained states through which one can tune the nonclassicality criteria appropriately.Setting intensity-dependent coupling function equal to 1 reduces the results to the constant coupling case. By comparing the latter case with the nonlinear regime, we will observe that the nonlinearity disappears the pattern of collapse-revival phenomenon in the evolution of Mandel parameter and population inversion(which can be seen in the linear case with constant coupling), however, more typical collapse-revivals will be appeared for the cross-correlation function in the nonlinear case. Finally, in both linear and nonlinear regime, the entropy remains less than(but close to) 0.5. In other words the particular chosen nonlinearity does not critically affect on the entropy of the system.展开更多
Proposal for the teleportation of two-atom state is presented. It is based on the simultaneous interaction of two two-level atoms with a single-mode cavity with a filed of n photons. In the proposed scheme, two pairs ...Proposal for the teleportation of two-atom state is presented. It is based on the simultaneous interaction of two two-level atoms with a single-mode cavity with a filed of n photons. In the proposed scheme, two pairs of EPR state are used as quantum channel to teleport an unknown two-atom state. The completed time is greatly reduced and cavity field is not required to be detected are shown to be the distinct features of the presented scheme.展开更多
The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after ...The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after colliding with the wall and the distribution of the field inside the vapour corresponds to L/λ, with L the thickness of the film and λ the incident wavelength. We find that the sub-Doppler structure is manifest both for normal incidence and small angle oblique incidence, It is feasible to detect the real part of selective reflection in several cases that have not been achieved before.展开更多
We propose a scheme to simultaneously achieve nonreciprocal conventional photon blockade(NCPB) and unconventional photon blockade(NUPB) in a spinning resonator coupled to two two-level atoms. We show that, with the un...We propose a scheme to simultaneously achieve nonreciprocal conventional photon blockade(NCPB) and unconventional photon blockade(NUPB) in a spinning resonator coupled to two two-level atoms. We show that, with the unequal frequency detuning of cavity and atoms from the driving laser, the quantum efect of the nonreciprocal photon blockade can be realized based on two regimes under diferent driving strengths. We confirm that, the NUPB results from the quantum destructive interference between distinct pathways when the driving laser is loaded from one side, whereas the destructive interference is broken when the system is driven from the other side. Moreover, the NCPB originates from whether the single excitation resonance condition is satisfied, corresponding to the opposite driving direction in contrast to the former. Besides, we obtain the optimal nonreciprocal results by appropriately choosing the system parameters. Interestingly, the UPB exhibits stronger robustness to thermal noises,and the nonreciprocity still exists up to a high thermal excitation. This work provides an alternative way to achieve nonreciprocal quantum devices based on the nonreciprocal photon blockade, which may help to develop information network processing.展开更多
Lithium-sulfur (Li-S) batteries have gained great attention due to the high theoretical energy density and low cost,yet their further commercialization has been obstructed by the notorious shuttle effect and sluggish ...Lithium-sulfur (Li-S) batteries have gained great attention due to the high theoretical energy density and low cost,yet their further commercialization has been obstructed by the notorious shuttle effect and sluggish redox dynamics.Herein,we supply a strategy to optimize the electron structure of Ni_(2)P by concurrently introducing B-doped atoms and P vacancies in Ni_(2)P (Vp-B-Ni_(2)P),thereby enhancing the bidirectional sulfur conversion.The study indicates that the simultaneous introduction of B-doped atoms and P vacancies in Ni_(2)P causes the redistribution of electron around Ni atoms,bringing about the upward shift of d-band center of Ni atoms and effective d-p orbital hybridization between Ni atoms and sulfur species,thus strengthening the chemical anchoring for lithium polysulfides (LiPSs) as well as expediting the bidirectional conversion kinetics of sulfur species.Meanwhile,theoretical calculations reveal that the incorporation of B-doped atoms and P vacancies in Ni_(2)P selectively promotes Li2S dissolution and nucleation processes.Thus,the Li-S batteries with Vp-B-Ni_(2)P-separators present outstanding rate ability of 777 m A h g^(-1)at 5 C and high areal capacity of 8.03 mA h cm^(-2)under E/S of 5μL mg^(-1)and sulfur loading of 7.20 mg cm^(-2).This work elucidates that introducing heteroatom and vacancy in metal phosphide collaboratively regulates the electron structure to accelerate bidirectional sulfur conversion.展开更多
We present the experimental demonstration of nondestructive detection of ^(171)Yb atoms in a magneto-optical trap(MOT) based on phase shift measurement induced by the atoms on a weak off-resonant laser beam. After loa...We present the experimental demonstration of nondestructive detection of ^(171)Yb atoms in a magneto-optical trap(MOT) based on phase shift measurement induced by the atoms on a weak off-resonant laser beam. After loading a green MOT of ^(171)Yb atoms, the phase shift is obtained with a two-color Mach–Zehnder interferometer by means of ±45 MHz detuning with respect to the ^(1)S_(0)–^(1)P_(1) transition. We measured a phase shift of about 100 mrad corresponding to an atom count of around 5 × 10^(5). This demonstrates that it is possible to obtain the number of atoms without direct destructive measurement compared with the absorption imaging method. This scheme could be an important approach towards a high-precision lattice clock for clock operation through suppression of the impact of the Dick effect.展开更多
Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a chall...Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a challenge in current research.This work proposed a one-step thermal copolymerization to obtain Cu(Ⅰ)doping porous carbon nitride(CUCN)through a spontaneously reducing atmosphere by urea in a covered crucible.The obtained CUCN had crumpled ultrathin nanosheets and mesoporous structures,which possessed higher specific surface areas than PCN.From X-ray absorption near edge structure(XANES)and Fourier transform extended X-ray absorption fine structure(FT-EXAFS)spectra analysis,the Cu doping existed in the oxidation state of Cu(Ⅰ)as single atoms anchored on the 2D layers of CN through two N neighbors,thereby facilitating efficient pathways for the transfer of photoexcited charge carriers.Furthermore,the photoluminescence(PL)spectra,electrochemical impedance spectra(EIS)and transient photocurrent response test proved the improved separation and transfer of photoexcited charge carriers for Cu(Ⅰ)introduction.Consequently,the photocatalytic activity of CUCN was much better than that of PCN for antibiotics norfloxacin(NOR),with 4.7-fold higher degradation reaction rate constants.From species-trapping experiments and density function theory(DFT)calculations,the Cu single atoms in Cu-N_(2)served as catalytic sites that could accelerate charge transfer and facilitate the adsorption of molecular oxygen to produce active species.The stable Cu(Ⅰ)embedded in the layer structure led to the excellent recycling test and remained stable after four runs of degradation and even thermal regenerated treatment.The degradation paths of NOR by CUCN under visible light were also demonstrated.Our work sheds light on a sustainable and practical approach for achieving stable metal single-atom doping and enhancing photocatalytic degradation of aqueous pollutants.展开更多
Atmospheric escape plays a critical role in shaping the long-term climate evolution of Mars.Among the various escape mechanisms,energetic neutral atoms(ENAs)generated through charge exchange between solar wind ions an...Atmospheric escape plays a critical role in shaping the long-term climate evolution of Mars.Among the various escape mechanisms,energetic neutral atoms(ENAs)generated through charge exchange between solar wind ions and exospheric neutrals serve as an important diagnostic for ion-neutral interactions and upper atmospheric loss.This study presents direct observations of hydrogen ENAs(H-ENAs)on the dayside of Mars by using the Mars Ion and Neutral Particle Analyzer(MINPA)onboard China’s Tianwen-1 orbiter.By analyzing H-ENA data during a coronal mass ejection and a stream interaction region from December 29,2021,to January 1,2022,and comparing these data with MAVEN/SWIA(Mars Atmosphere and Volatile EvolutioN/Solar Wind Ion Analyzer)solar wind measurements,we examine the temporal evolution of H-ENA flux and the associated sputtered escape of atmospheric constituents.The observed H-ENA velocity is consistent with upstream solar wind ions,and the H-ENA-to-ion intensity ratio is used to infer variations in exospheric density,revealing a delayed response to enhanced solar wind activity.Penetrating H-ENA intensities reach up to 5.3×10^(6)s^(−1) cm^(−2),with energy fluxes on the order of(0.5-8.1)×10^(−3) mW/m^(2).The estimated oxygen sputtered escape rate driven by penetrating H-ENAs ranges from 5.5×10^(23)s^(−1) to 5.2×10^(24)s^(−1),comparable to or exceeding previous estimates based on penetrating ions.The findings highlight the need for low-altitude H-ENA observations to better quantify their atmospheric interactions and refine our understanding of nonthermal escape processes at Mars.展开更多
Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupli...Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupling constants between atoms,the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed.The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms,the atomic initial states and the photon number of transition.The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is β11〉.When the initial state of two atoms is β01〉,the entanglement of two atoms displays periodic oscillation behavior.And its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.On the other hand,when the initial state is β00〉 or β10〉,the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.展开更多
Translator’s Note:Shou Chin Wang(Wang Shoujing)was one of the few Chinese physicists who made significant contributions to the early development of quantum mechanics.One of his representative works is the study on th...Translator’s Note:Shou Chin Wang(Wang Shoujing)was one of the few Chinese physicists who made significant contributions to the early development of quantum mechanics.One of his representative works is the study on the van der Waals potential based on quantum mechanics.Specifically,using the second-order perturbation theory in quantum mechanics,he derived a long-range attractive potential of the form−1/R6 between two widely separated atoms.Since individual atoms are non-polar,meaning their average dipole moments are zero,this interaction arises from fluctuations in the instantaneous electric dipole moments of the two atoms.展开更多
Conversion between different types of entangled states is an interesting problem in quantum mechanics.But research on the conversion between the Greenberger-Horne-Zeilinger(GHZ)state and Knill-Laflamme-Milburn(KLM)sta...Conversion between different types of entangled states is an interesting problem in quantum mechanics.But research on the conversion between the Greenberger-Horne-Zeilinger(GHZ)state and Knill-Laflamme-Milburn(KLM)state in an atomic system has not been reported.In this paper,we propose a scheme to realize the interconversion(one-step)between the GHZ state and KLM state with Rydberg atoms.By utilizing Rydberg-mediated interactions,we simplify the system.By combining a Lie-transform-based pulse design,the evolution path is built up to realize interconversion of the GHZ state and KLM state.The numerical simulation result shows that the present scheme is robust against decoherence and operational imperfection.展开更多
The introduction of metal single atoms(SAs)and nanoparticles(NPs)are effective approaches to mod-ify electronic configuration of semiconductors,whereas recognizing the synergistic effects of metal SAs and NPs are stil...The introduction of metal single atoms(SAs)and nanoparticles(NPs)are effective approaches to mod-ify electronic configuration of semiconductors,whereas recognizing the synergistic effects of metal SAs and NPs are still challenging in photocatalytic water purification.Herein,a general strategy is achieved by subsequentially anchoring Fe SAs and Fe NPs in graphitic carbon nitride.The modification of Fe SAs and Fe NPs improves the energy band structure and constructs a gradient charge polarization,directly expanding the optical absorption range and facilitating the efficient separation and transfer of charge car-riers.With the assistance of the gradient charge polarization,pollutants are readily oxidated by h+,which strengthens the continuous reduction of O2 on Fe NPs for pollutant oxidation in water.This work rein-forces the synergistic effect of SAs and NPs on electronic configuration modulation at the atomic level,which exhibits great potential for the construction of an efficient and sustainable water purification sys-tem.展开更多
Metal nanoparticles,clusters,and single atoms exhibit remarkable variations in catalytic performance due to their different electronic and atomic structures.To explore the size-dependent effects on acetylene hydrochlo...Metal nanoparticles,clusters,and single atoms exhibit remarkable variations in catalytic performance due to their different electronic and atomic structures.To explore the size-dependent effects on acetylene hydrochlorination,a series of Ru catalysts(including single atoms(Ru SAC CS),clusters(Ru ACs CS),and nanoparticles(Ru NPs CS)catalysts)were accurately synthesized by a defect-engineering strategy.Ru SAC CS demonstrated the optimal catalytic performance.The structural–activity relationship between the catalyst’s initial activity and charge,Ru–Ru coordination number and the oxidation state of Ru sites offer insights into how the structure of Ru active sites affects acetylene hydrochlorination at the atomic scale.Density functional theory(DFT)simulations reveal that the energy barrier for the rate-determine-step(*Cl approaching the*CH_(2)=CH intermediate to form*C_(2)H_(3)Cl)for Ru SAC CS is significantly lower,facilitating barrier overcoming and enhancing vinyl chloride formation.Furthermore,Ru SAC CS displays suitable adsorption energies for C2H2 and C2H3Cl,which is conducive to prevent coke deposition and enhance the catalytic stability.This research demonstrates the efficiency of Ru single-atom catalysts for acetylene hydrochlorination and offers new perspectives on the precise construction and catalytic mechanism of sub-nanometer catalysts.展开更多
The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-a...The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-atom anchored on the defective carbon nitride structure(Cu SA/Def-CN)is designed for selective photocatalytic oxidation of methane into methanol using O_(2) under mild conditions.The Cu SA/Def-CN catalyst exhibits a high methanol selectivity of 92.8%under optimized conditions.Mechanistic studies reveal a synergistic effect between Def-CN and Cu SA,where Def-CN is responsible for the in-situ generation of hydrogen peroxide,which is subsequently decomposed by the Cu SA sites to produce·OH radicals that play a key role in the rate-determining step of methane activation to form methanol.Additionally,the presence of Cu SA not only enhances the electron-hole separation efficiency and improves the transfer of the photo-generated charges,but also increases the number of active sites for methane adsorption and activation.These insights provide valuable guidance for designing efficient catalysts for the highly selective photocatalytic oxidation of methane to methanol.展开更多
We propose a scheme for dual-species deceleration and trapping of a cold atom–molecule mixture by a frequency chirping stimulated force.We study the stimulated force exerted on Mg F and Rb using optical Bloch equatio...We propose a scheme for dual-species deceleration and trapping of a cold atom–molecule mixture by a frequency chirping stimulated force.We study the stimulated force exerted on Mg F and Rb using optical Bloch equations based on a direct numerical solution for the time-dependent density matrix.We analyze the relationship between the frequency chirping rate and the number of Mg F molecules and Rb atoms.In addition,we study the dynamical process of molecular deceleration and the effect of transverse diffusion.Monte–Carlo simulations show that buffer-gas-cooled Mg F and Rb beams,with initial velocities of 200 m/s and 130 m/s respectively,can be decelerated to less than 10 m/s.This is achieved with laser powers of as low as 357 m W for Mg F and 10 m W for Rb per traveling wave.The rapid deceleration minimizes molecular loss due to transverse diffusion during the deceleration process.The estimated number of molecules that can be trapped in a magneto-optical trap(MOT)is about 9.0×10^(6),which is an order of magnitude larger than the number of Mg F molecules decelerated by the spontaneous radiation force.The results offer a promising starting point for further studies of sympathetic cooling.展开更多
Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duct...Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duction to H_(2)O_(2),it is a challenge for polymeric photocatalysts to achieve efficient photocatalytic H_(2)O_(2) production.Herein,Ag single atoms and nitrogen defects decorated carbon nitride(Ag@MCT)are con-structed through self-assembly and pyrolysis methods.The optimized photocatalyst displays exceptional performance in pure water,with an H_(2)O_(2) production rate of as high as 528.4μmol g^(-1) h^(-1) and an apparent quantum yield for H_(2)O_(2)production of 4.5%at 420 nm.Experimental and theoretical results reveal that the Ag atomic sites act as electron mediators that promote the capture and transfer of photo-generated charge carriers,while nitrogen defects as electron collectors and reaction sites to enhance the adsorption and activation of O_(2),accelerating reduction kinetics from O_(2) to H_(2)O_(2).This work presents a re-liable strategy to design excellent photocatalysts by rationally modulating electronic structures and active sites for accelerating photo-generated charge carriers transfer and surface reaction kinetics.展开更多
The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportio...The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportion remains one challenge for the catalyst design.Herein,a Ni2+-loaded porous poly(ionic liquids)(PIL)precursor synthesized through the free radical self-polymerization of the ionic liquid monomer,1-allyl-3-vinylimidazolium chloride,was pyrolyzed to prepare the Ni,N co-doped carbon materials,in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing temperature.The catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO_(2)into CO.Operando Ni K-edge X-ray absorption near-edge structure(XANES)spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and NPs.The charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active sites.In the electroreduction of CO_(2),the coexistence of Ni SAs and NPs strengthened the CO_(2)activation and the affinity towards the key intermediate of*COOH,lowering the free energy for the potential-determining*CO_(2)→*COOH step,and therefore promoted the catalysis efficiency.展开更多
In this paper we study the dynamics of the atomic inversion, von Neumann entropy and entropy squeezing for moving and non-moving two-level atoms interacting with a Perelomov coherent state. The final state of the syst...In this paper we study the dynamics of the atomic inversion, von Neumann entropy and entropy squeezing for moving and non-moving two-level atoms interacting with a Perelomov coherent state. The final state of the system using specific initial conditions is obtained. The effects of Perelomov and detuning parameters are examined in the absence and presence of the atomic motion. Important phenomena such as the collapse and revival are shown to be very sensitive to the variation of the Perelomov parameter in the presence of detuning parameter. The results show that the Perelomov parameter is very useful in generating a high amount of entanglement due to variation of the detuning parameter.展开更多
Solid strong base catalysts have high potentials in a variety of reactions due to the advantages of negligible corrosion,easy separation,and high efficiency.However,two issues hinder the applications of such catalysts...Solid strong base catalysts have high potentials in a variety of reactions due to the advantages of negligible corrosion,easy separation,and high efficiency.However,two issues hinder the applications of such catalysts seriously,namely aggregation of basic sites and leaching of active species during reactions.The development of solid strong base catalysts with active sites that are highly dispersed and stable remains a pronounced challenge.In this work,we employed a two-step reduction strategy to anchor Na single atoms on nitrogen-doped porous carbon(NPC)support,producing a high-performance solid strongly basic catalyst named as Na1/NPC.The alkali precursor NaNO3was converted to Na_(2)O on NPC at 400℃,in which conventional solid base catalyst Na_(2)O/NPC was generated.Upon heat treatment at 850oC,Na_(2)O was further reduced to Na single atoms anchored on NPC,creating Na1/NPC.Experimental studies and theoretical calculations show that Na is structurally embedded on the support in penta-coordinated configuration(Na-C_(3)N_(2)).The synergistic effect of highly dispersed Na atoms and nitrogen doping results in uncommon catalytic activity and stability.In transesterification between methanol and ethylene carbonate to produce dimethyl carbonate(DMC),the yield of DMC reaches 48.4%over Na1/NPC,corresponding to a turnover frequency(TOF)of 129.4 h^(-1),which is far beyond the conventional counterpart Na_(2)O/NPC(63.3 h^(-1))and various reported solid base catalysts.The catalytic activity of Na1/NPC almost keeps constant during five cycles,while 87%of activity is lost for Na_(2)O/NPC due to the leaching of basic sites.This work might offer new ideas for the development of efficient single-atom solid strong base catalysts with high efficiency.展开更多
文摘Herein, we present an approach to look for the best phenomenon to measure quantum correlation. The system of two isolated qubits each interacting with a single-mode cavity was theoretically created to study the quantum correlation. Some of the phenomena, such as the quantum discord and concurrence, were generated through such a system. The influences of initial state purity, qubit motion, and detuning parameters were discussed for the phenomena. These parameters for a specific value show that the behavior of phenomena are analogous. It is interesting to mention that some values of detuning undergo a sudden death of phenomena, and the quantum discord still captures the qubits quantum correlation. We predict that the quantum discord may be a better measure of quantum correlation than concurrence.
文摘In this paper, we consider the interaction between two two-level atoms and a two-mode binomial field with a general intensity-dependent coupling regime. The outlined dynamical problem has explicit analytical solution, by which we can evaluate a few of its physical features of interest. To achieve the purpose of the paper, after choosing a particular nonlinearity function, we investigate the quantum statistics, atomic population inversion and at last the linear entropy of the atom-field system which is a good measure for the degree of entanglement. In detail, the effects of binomial field parameters, in addition to different initial atomic states on the temporal behavior of the mentioned quantities have been analyzed. The results show that, the values of binomial field parameters and the initial state of the two atoms influence on the nonclassical effects in the obtained states through which one can tune the nonclassicality criteria appropriately.Setting intensity-dependent coupling function equal to 1 reduces the results to the constant coupling case. By comparing the latter case with the nonlinear regime, we will observe that the nonlinearity disappears the pattern of collapse-revival phenomenon in the evolution of Mandel parameter and population inversion(which can be seen in the linear case with constant coupling), however, more typical collapse-revivals will be appeared for the cross-correlation function in the nonlinear case. Finally, in both linear and nonlinear regime, the entropy remains less than(but close to) 0.5. In other words the particular chosen nonlinearity does not critically affect on the entropy of the system.
文摘Proposal for the teleportation of two-atom state is presented. It is based on the simultaneous interaction of two two-level atoms with a single-mode cavity with a filed of n photons. In the proposed scheme, two pairs of EPR state are used as quantum channel to teleport an unknown two-atom state. The completed time is greatly reduced and cavity field is not required to be detected are shown to be the distinct features of the presented scheme.
基金Project supported by Science Foundation of Ningxia Higher Education of China （Grant No 2005153）.
文摘The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after colliding with the wall and the distribution of the field inside the vapour corresponds to L/λ, with L the thickness of the film and λ the incident wavelength. We find that the sub-Doppler structure is manifest both for normal incidence and small angle oblique incidence, It is feasible to detect the real part of selective reflection in several cases that have not been achieved before.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12074330, 62071412, and 12074094)。
文摘We propose a scheme to simultaneously achieve nonreciprocal conventional photon blockade(NCPB) and unconventional photon blockade(NUPB) in a spinning resonator coupled to two two-level atoms. We show that, with the unequal frequency detuning of cavity and atoms from the driving laser, the quantum efect of the nonreciprocal photon blockade can be realized based on two regimes under diferent driving strengths. We confirm that, the NUPB results from the quantum destructive interference between distinct pathways when the driving laser is loaded from one side, whereas the destructive interference is broken when the system is driven from the other side. Moreover, the NCPB originates from whether the single excitation resonance condition is satisfied, corresponding to the opposite driving direction in contrast to the former. Besides, we obtain the optimal nonreciprocal results by appropriately choosing the system parameters. Interestingly, the UPB exhibits stronger robustness to thermal noises,and the nonreciprocity still exists up to a high thermal excitation. This work provides an alternative way to achieve nonreciprocal quantum devices based on the nonreciprocal photon blockade, which may help to develop information network processing.
基金Institute of Technology Research Fund Program for Young Scholars21C Innovation Laboratory Contemporary Amperex Technology Co.,Limited,Ninde, 352100, China (21C–OP-202314)。
文摘Lithium-sulfur (Li-S) batteries have gained great attention due to the high theoretical energy density and low cost,yet their further commercialization has been obstructed by the notorious shuttle effect and sluggish redox dynamics.Herein,we supply a strategy to optimize the electron structure of Ni_(2)P by concurrently introducing B-doped atoms and P vacancies in Ni_(2)P (Vp-B-Ni_(2)P),thereby enhancing the bidirectional sulfur conversion.The study indicates that the simultaneous introduction of B-doped atoms and P vacancies in Ni_(2)P causes the redistribution of electron around Ni atoms,bringing about the upward shift of d-band center of Ni atoms and effective d-p orbital hybridization between Ni atoms and sulfur species,thus strengthening the chemical anchoring for lithium polysulfides (LiPSs) as well as expediting the bidirectional conversion kinetics of sulfur species.Meanwhile,theoretical calculations reveal that the incorporation of B-doped atoms and P vacancies in Ni_(2)P selectively promotes Li2S dissolution and nucleation processes.Thus,the Li-S batteries with Vp-B-Ni_(2)P-separators present outstanding rate ability of 777 m A h g^(-1)at 5 C and high areal capacity of 8.03 mA h cm^(-2)under E/S of 5μL mg^(-1)and sulfur loading of 7.20 mg cm^(-2).This work elucidates that introducing heteroatom and vacancy in metal phosphide collaboratively regulates the electron structure to accelerate bidirectional sulfur conversion.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. U20A2075,11803072,and 12374467)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0300902)the Hubei Provincial Science and Technology Major Project (Grant No. ZDZX2022000004)。
文摘We present the experimental demonstration of nondestructive detection of ^(171)Yb atoms in a magneto-optical trap(MOT) based on phase shift measurement induced by the atoms on a weak off-resonant laser beam. After loading a green MOT of ^(171)Yb atoms, the phase shift is obtained with a two-color Mach–Zehnder interferometer by means of ±45 MHz detuning with respect to the ^(1)S_(0)–^(1)P_(1) transition. We measured a phase shift of about 100 mrad corresponding to an atom count of around 5 × 10^(5). This demonstrates that it is possible to obtain the number of atoms without direct destructive measurement compared with the absorption imaging method. This scheme could be an important approach towards a high-precision lattice clock for clock operation through suppression of the impact of the Dick effect.
基金supported by the National Natural Science Foundation of China(Nos.52070103 and 22102102)Zhejiang Provincial Natural Science Foundation of China(Nos.LY21E090004 and LQ22B050004)+1 种基金Ningbo Public Welfare Science and Technology Program(No.2021S025)Ningbo Youth Leading Talent Project(No.2024QL038).
文摘Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a challenge in current research.This work proposed a one-step thermal copolymerization to obtain Cu(Ⅰ)doping porous carbon nitride(CUCN)through a spontaneously reducing atmosphere by urea in a covered crucible.The obtained CUCN had crumpled ultrathin nanosheets and mesoporous structures,which possessed higher specific surface areas than PCN.From X-ray absorption near edge structure(XANES)and Fourier transform extended X-ray absorption fine structure(FT-EXAFS)spectra analysis,the Cu doping existed in the oxidation state of Cu(Ⅰ)as single atoms anchored on the 2D layers of CN through two N neighbors,thereby facilitating efficient pathways for the transfer of photoexcited charge carriers.Furthermore,the photoluminescence(PL)spectra,electrochemical impedance spectra(EIS)and transient photocurrent response test proved the improved separation and transfer of photoexcited charge carriers for Cu(Ⅰ)introduction.Consequently,the photocatalytic activity of CUCN was much better than that of PCN for antibiotics norfloxacin(NOR),with 4.7-fold higher degradation reaction rate constants.From species-trapping experiments and density function theory(DFT)calculations,the Cu single atoms in Cu-N_(2)served as catalytic sites that could accelerate charge transfer and facilitate the adsorption of molecular oxygen to produce active species.The stable Cu(Ⅰ)embedded in the layer structure led to the excellent recycling test and remained stable after four runs of degradation and even thermal regenerated treatment.The degradation paths of NOR by CUCN under visible light were also demonstrated.Our work sheds light on a sustainable and practical approach for achieving stable metal single-atom doping and enhancing photocatalytic degradation of aqueous pollutants.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42188101, 42274211, 41974170, 42374184, 42122032, and 41974196)the Chinese Academy of Sciences (Grant Nos. QYZDJSSW-JSC028, XDA15052500, XDA17010301, and XDB41000000)+3 种基金the CNSA (Grant No. D050103)the Specialized Research Fund for State Key Laboratories of Chinathe Specialized Research Fund for Laboratory of Geospace Environment of the University of Science and Technology of Chinasupported by the International Space Science Institute (ISSI) in Bern and Beijing through the ISSI/ISSI-BJ International Team Project titled “Understanding the Mars Space Environment Through Multi-Spacecraft Measurements” (ISSI Team Project No. 23-582 and ISSI-BJ Team Project No. 58)
文摘Atmospheric escape plays a critical role in shaping the long-term climate evolution of Mars.Among the various escape mechanisms,energetic neutral atoms(ENAs)generated through charge exchange between solar wind ions and exospheric neutrals serve as an important diagnostic for ion-neutral interactions and upper atmospheric loss.This study presents direct observations of hydrogen ENAs(H-ENAs)on the dayside of Mars by using the Mars Ion and Neutral Particle Analyzer(MINPA)onboard China’s Tianwen-1 orbiter.By analyzing H-ENA data during a coronal mass ejection and a stream interaction region from December 29,2021,to January 1,2022,and comparing these data with MAVEN/SWIA(Mars Atmosphere and Volatile EvolutioN/Solar Wind Ion Analyzer)solar wind measurements,we examine the temporal evolution of H-ENA flux and the associated sputtered escape of atmospheric constituents.The observed H-ENA velocity is consistent with upstream solar wind ions,and the H-ENA-to-ion intensity ratio is used to infer variations in exospheric density,revealing a delayed response to enhanced solar wind activity.Penetrating H-ENA intensities reach up to 5.3×10^(6)s^(−1) cm^(−2),with energy fluxes on the order of(0.5-8.1)×10^(−3) mW/m^(2).The estimated oxygen sputtered escape rate driven by penetrating H-ENAs ranges from 5.5×10^(23)s^(−1) to 5.2×10^(24)s^(−1),comparable to or exceeding previous estimates based on penetrating ions.The findings highlight the need for low-altitude H-ENA observations to better quantify their atmospheric interactions and refine our understanding of nonthermal escape processes at Mars.
基金Supported by the Natural Science Foundation of Fujian Province under Grant (No.2008J0217)
文摘Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupling constants between atoms,the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed.The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms,the atomic initial states and the photon number of transition.The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is β11〉.When the initial state of two atoms is β01〉,the entanglement of two atoms displays periodic oscillation behavior.And its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.On the other hand,when the initial state is β00〉 or β10〉,the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.
文摘Translator’s Note:Shou Chin Wang(Wang Shoujing)was one of the few Chinese physicists who made significant contributions to the early development of quantum mechanics.One of his representative works is the study on the van der Waals potential based on quantum mechanics.Specifically,using the second-order perturbation theory in quantum mechanics,he derived a long-range attractive potential of the form−1/R6 between two widely separated atoms.Since individual atoms are non-polar,meaning their average dipole moments are zero,this interaction arises from fluctuations in the instantaneous electric dipole moments of the two atoms.
基金supported by the Department of Education of Liaoning Province(Grant Nos.LJKZ1015,LJ2020005,LJKZZ20220120)the Natural Science Foundation of Liaoning Province(Grant Nos.2020-BS-234,2021-MS-317,2022-MS-372)the Program of Liaoning Bai Qian Wan Talents Program(Grant No.2021921096)。
文摘Conversion between different types of entangled states is an interesting problem in quantum mechanics.But research on the conversion between the Greenberger-Horne-Zeilinger(GHZ)state and Knill-Laflamme-Milburn(KLM)state in an atomic system has not been reported.In this paper,we propose a scheme to realize the interconversion(one-step)between the GHZ state and KLM state with Rydberg atoms.By utilizing Rydberg-mediated interactions,we simplify the system.By combining a Lie-transform-based pulse design,the evolution path is built up to realize interconversion of the GHZ state and KLM state.The numerical simulation result shows that the present scheme is robust against decoherence and operational imperfection.
基金the National Natural Science Foundation of China(Nos.52100032 and 52350005)the Basic and Applied Basic Research Project of Guangzhou(Nos.2024A04J3679, 2024A03J0088)+2 种基金the Introduced Innovative Research and Development Team Project under the“The Pearl River Talent Recruitment Program”of Guangdong Province(No.2019ZT08L387)the Special Basic Research Fund for Central Public Research Institutes of China(No.PMzx703-202204-152)the Research Fund Program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology(No.2023B1212060016).
文摘The introduction of metal single atoms(SAs)and nanoparticles(NPs)are effective approaches to mod-ify electronic configuration of semiconductors,whereas recognizing the synergistic effects of metal SAs and NPs are still challenging in photocatalytic water purification.Herein,a general strategy is achieved by subsequentially anchoring Fe SAs and Fe NPs in graphitic carbon nitride.The modification of Fe SAs and Fe NPs improves the energy band structure and constructs a gradient charge polarization,directly expanding the optical absorption range and facilitating the efficient separation and transfer of charge car-riers.With the assistance of the gradient charge polarization,pollutants are readily oxidated by h+,which strengthens the continuous reduction of O2 on Fe NPs for pollutant oxidation in water.This work rein-forces the synergistic effect of SAs and NPs on electronic configuration modulation at the atomic level,which exhibits great potential for the construction of an efficient and sustainable water purification sys-tem.
基金supported by the National Natural Science Foundation of China(Nos.21706167 and 22068031)the Tianchi Talent Project of Xinjiang Uygur Autonomous Region,High-Level Talents Launching Program of Shihezi University(No.2022ZK002)+2 种基金Youth Innovation Cultivation Talents Program of Shihezi University(No.CXPY202202)Open project of Shihezi University(No.KF202202)Scientific and Technological Project of Yunnan Precious Metals Laboratory(No.YP2023050202).
文摘Metal nanoparticles,clusters,and single atoms exhibit remarkable variations in catalytic performance due to their different electronic and atomic structures.To explore the size-dependent effects on acetylene hydrochlorination,a series of Ru catalysts(including single atoms(Ru SAC CS),clusters(Ru ACs CS),and nanoparticles(Ru NPs CS)catalysts)were accurately synthesized by a defect-engineering strategy.Ru SAC CS demonstrated the optimal catalytic performance.The structural–activity relationship between the catalyst’s initial activity and charge,Ru–Ru coordination number and the oxidation state of Ru sites offer insights into how the structure of Ru active sites affects acetylene hydrochlorination at the atomic scale.Density functional theory(DFT)simulations reveal that the energy barrier for the rate-determine-step(*Cl approaching the*CH_(2)=CH intermediate to form*C_(2)H_(3)Cl)for Ru SAC CS is significantly lower,facilitating barrier overcoming and enhancing vinyl chloride formation.Furthermore,Ru SAC CS displays suitable adsorption energies for C2H2 and C2H3Cl,which is conducive to prevent coke deposition and enhance the catalytic stability.This research demonstrates the efficiency of Ru single-atom catalysts for acetylene hydrochlorination and offers new perspectives on the precise construction and catalytic mechanism of sub-nanometer catalysts.
文摘The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-atom anchored on the defective carbon nitride structure(Cu SA/Def-CN)is designed for selective photocatalytic oxidation of methane into methanol using O_(2) under mild conditions.The Cu SA/Def-CN catalyst exhibits a high methanol selectivity of 92.8%under optimized conditions.Mechanistic studies reveal a synergistic effect between Def-CN and Cu SA,where Def-CN is responsible for the in-situ generation of hydrogen peroxide,which is subsequently decomposed by the Cu SA sites to produce·OH radicals that play a key role in the rate-determining step of methane activation to form methanol.Additionally,the presence of Cu SA not only enhances the electron-hole separation efficiency and improves the transfer of the photo-generated charges,but also increases the number of active sites for methane adsorption and activation.These insights provide valuable guidance for designing efficient catalysts for the highly selective photocatalytic oxidation of methane to methanol.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174115 and 91836103)。
文摘We propose a scheme for dual-species deceleration and trapping of a cold atom–molecule mixture by a frequency chirping stimulated force.We study the stimulated force exerted on Mg F and Rb using optical Bloch equations based on a direct numerical solution for the time-dependent density matrix.We analyze the relationship between the frequency chirping rate and the number of Mg F molecules and Rb atoms.In addition,we study the dynamical process of molecular deceleration and the effect of transverse diffusion.Monte–Carlo simulations show that buffer-gas-cooled Mg F and Rb beams,with initial velocities of 200 m/s and 130 m/s respectively,can be decelerated to less than 10 m/s.This is achieved with laser powers of as low as 357 m W for Mg F and 10 m W for Rb per traveling wave.The rapid deceleration minimizes molecular loss due to transverse diffusion during the deceleration process.The estimated number of molecules that can be trapped in a magneto-optical trap(MOT)is about 9.0×10^(6),which is an order of magnitude larger than the number of Mg F molecules decelerated by the spontaneous radiation force.The results offer a promising starting point for further studies of sympathetic cooling.
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.52488201)the National Natural Science Foundation of China(No.52276213)+1 种基金the Key Research and Development Program of Shaanxi Province(No.2024GX-YBXM-459)the Fundamental Research Funds for the Central Universities.
文摘Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duction to H_(2)O_(2),it is a challenge for polymeric photocatalysts to achieve efficient photocatalytic H_(2)O_(2) production.Herein,Ag single atoms and nitrogen defects decorated carbon nitride(Ag@MCT)are con-structed through self-assembly and pyrolysis methods.The optimized photocatalyst displays exceptional performance in pure water,with an H_(2)O_(2) production rate of as high as 528.4μmol g^(-1) h^(-1) and an apparent quantum yield for H_(2)O_(2)production of 4.5%at 420 nm.Experimental and theoretical results reveal that the Ag atomic sites act as electron mediators that promote the capture and transfer of photo-generated charge carriers,while nitrogen defects as electron collectors and reaction sites to enhance the adsorption and activation of O_(2),accelerating reduction kinetics from O_(2) to H_(2)O_(2).This work presents a re-liable strategy to design excellent photocatalysts by rationally modulating electronic structures and active sites for accelerating photo-generated charge carriers transfer and surface reaction kinetics.
基金National Natural Science Foundation of China(grants 22072065,22178162,and 22222806)Distinguished Youth Foundation of Jiangsu Province(grant BK20220053)Six talent peaks project in Jiangsu Province(grant JNHB-035)。
文摘The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportion remains one challenge for the catalyst design.Herein,a Ni2+-loaded porous poly(ionic liquids)(PIL)precursor synthesized through the free radical self-polymerization of the ionic liquid monomer,1-allyl-3-vinylimidazolium chloride,was pyrolyzed to prepare the Ni,N co-doped carbon materials,in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing temperature.The catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO_(2)into CO.Operando Ni K-edge X-ray absorption near-edge structure(XANES)spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and NPs.The charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active sites.In the electroreduction of CO_(2),the coexistence of Ni SAs and NPs strengthened the CO_(2)activation and the affinity towards the key intermediate of*COOH,lowering the free energy for the potential-determining*CO_(2)→*COOH step,and therefore promoted the catalysis efficiency.
文摘In this paper we study the dynamics of the atomic inversion, von Neumann entropy and entropy squeezing for moving and non-moving two-level atoms interacting with a Perelomov coherent state. The final state of the system using specific initial conditions is obtained. The effects of Perelomov and detuning parameters are examined in the absence and presence of the atomic motion. Important phenomena such as the collapse and revival are shown to be very sensitive to the variation of the Perelomov parameter in the presence of detuning parameter. The results show that the Perelomov parameter is very useful in generating a high amount of entanglement due to variation of the detuning parameter.
基金supported by the National Science Foundation of China(22125804 and U24A20534)。
文摘Solid strong base catalysts have high potentials in a variety of reactions due to the advantages of negligible corrosion,easy separation,and high efficiency.However,two issues hinder the applications of such catalysts seriously,namely aggregation of basic sites and leaching of active species during reactions.The development of solid strong base catalysts with active sites that are highly dispersed and stable remains a pronounced challenge.In this work,we employed a two-step reduction strategy to anchor Na single atoms on nitrogen-doped porous carbon(NPC)support,producing a high-performance solid strongly basic catalyst named as Na1/NPC.The alkali precursor NaNO3was converted to Na_(2)O on NPC at 400℃,in which conventional solid base catalyst Na_(2)O/NPC was generated.Upon heat treatment at 850oC,Na_(2)O was further reduced to Na single atoms anchored on NPC,creating Na1/NPC.Experimental studies and theoretical calculations show that Na is structurally embedded on the support in penta-coordinated configuration(Na-C_(3)N_(2)).The synergistic effect of highly dispersed Na atoms and nitrogen doping results in uncommon catalytic activity and stability.In transesterification between methanol and ethylene carbonate to produce dimethyl carbonate(DMC),the yield of DMC reaches 48.4%over Na1/NPC,corresponding to a turnover frequency(TOF)of 129.4 h^(-1),which is far beyond the conventional counterpart Na_(2)O/NPC(63.3 h^(-1))and various reported solid base catalysts.The catalytic activity of Na1/NPC almost keeps constant during five cycles,while 87%of activity is lost for Na_(2)O/NPC due to the leaching of basic sites.This work might offer new ideas for the development of efficient single-atom solid strong base catalysts with high efficiency.
