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
The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compa...The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.展开更多
We propose a scheme for realizing a controlled geometric phase gate for two neutral atoms.We apply thestimulated Raman adiabatic passage to transfer atoms from their ground states into Rydberg excited states, and use ...We propose a scheme for realizing a controlled geometric phase gate for two neutral atoms.We apply thestimulated Raman adiabatic passage to transfer atoms from their ground states into Rydberg excited states, and use theRydberg interaction induced energy shifts to generate geometric phase and construct quantum gates.展开更多
Violent galactic encounters or mergers are the leading contenders for triggering luminous quasar activity at low redshifts: such interactions can lead to the concentration of gas in the host galactic nucleus, thus fue...Violent galactic encounters or mergers are the leading contenders for triggering luminous quasar activity at low redshifts: such interactions can lead to the concentration of gas in the host galactic nucleus, thus fueling the suspected central superrmassive black hole. Although optical images show a number of violently interacting systems, in many cases the evidence for such interactions is only circumstantial (e.g., asymmetric optical morphologies, projected nearby companion galaxies) or not at all apparent. Here we image quasar host galaxies for the first time in the redshifted 21 cm line emission of neutral atomic hydrogen (HI) gas, which in nearby galaxies has proven to be a particularly sensitive as well as enduring tracer of tidal interactions. The three quasars studied have different optical environments normally seen around low reshift quasars, ranging from a perhaps mildly interacting system to a relatively undisturbed host with a projected neighbouring galaxy to an isolated and apparently serene host galaxy. By contrast with their optical appearences, all three quasar host galaxies exhibit ongoing or remnant tidal HI disruptions tracing galactic encounters or mergers. These observations provide a better understanding of the likely stage of their interaction.展开更多
Vast magnetospheric regions are mapped along the field lines to the narrow latitudinal band of the polar/auroral regions. Therefore monitoring of solar wind energy dissipation into the ionosphere at auroral latitudes ...Vast magnetospheric regions are mapped along the field lines to the narrow latitudinal band of the polar/auroral regions. Therefore monitoring of solar wind energy dissipation into the ionosphere at auroral latitudes gives unique opportunities to study geomagnetic disturbances in their complexity from a relatively well-localized vantage point. Here we introduce and present the current state of a recently proposed science project for coordinated monitoring of high-latitude activity with the EISCAT (European Incoherent Scatter) radar array supported by ground-based magnetometer and optical data and ENA (Energetic Neutral Atom) observation from the CINEMA (Cube-Sat for Ions, Neutrals, Electrons and Magnetic field) satellite system.展开更多
The spectrum and the wave function of neutral atoms in the magnetic field of a Kepler guide are presented by reducing a two dimensional stationary Schrdinger equation to a one dimensional hydrogen atom in Rydberg stat...The spectrum and the wave function of neutral atoms in the magnetic field of a Kepler guide are presented by reducing a two dimensional stationary Schrdinger equation to a one dimensional hydrogen atom in Rydberg states. In addition, we set the scale for the atomic orbits and binding energy in the quantum regime, and compare it with the outcome of the experiment. At the same time, we find that reducing the current and radius of the wire properly will increase the loading efficiency of the Kepler guide.展开更多
The grid-based energetic neutral atom imager(GENA)onboard the Queqiao-2 satellite is designed to capture high spatiotemporal resolution data of the Earth's ring current from a lunar orbit at a distance of 380000 k...The grid-based energetic neutral atom imager(GENA)onboard the Queqiao-2 satellite is designed to capture high spatiotemporal resolution data of the Earth's ring current from a lunar orbit at a distance of 380000 km.The instrument operates based on the time-of-flight(TOF)method and the grid-based encoding modulation principle.Key specifications of GENA include the following:detection of H atoms with an energy range of 4–200 keV,detection of O atoms with an energy range of 8–250 ke V,an energy resolution of better than 1 keV@10 keV,a field of view(FOV)of 19.72°×45.07°,an angular resolution of 0.43°,and a geometric factor of 19.2 cm^(2)sr.This paper presents some ground calibration results obtained during the testing of the proposed imager.GENA is expected to perform energetic neutral atom imaging of the Earth's magnetosphere and provide crucial data for studying particle injection from the magnetotail into the ring current region,as well as the generation and evolution of geomagnetic storms.展开更多
Coded aperture imaging(CAI)is widely used as an energetic-particles telescope in high-energy astrophysics.A typical CAI system consists of a coded mask(CM),a position-sensitive detector,and reconstruction algorithms t...Coded aperture imaging(CAI)is widely used as an energetic-particles telescope in high-energy astrophysics.A typical CAI system consists of a coded mask(CM),a position-sensitive detector,and reconstruction algorithms that recover the source distributions from the measured projections.The imaging performance of CAI largely depends on the CM design,which governs the field-of-view(FOV),spatial resolution,sensitivity,and signalto-noise ratio(SNR).展开更多
The imaging of terrestrial energetic neutral atoms(ENAs)is potentially a powerful way to reveal the large-scale characteristics and overall evolutions of the magnetosphere.The grid-based ENA(GENA)detector onboard Queq...The imaging of terrestrial energetic neutral atoms(ENAs)is potentially a powerful way to reveal the large-scale characteristics and overall evolutions of the magnetosphere.The grid-based ENA(GENA)detector onboard Queqiao-2 aims at providing global images of the main regions of ENA emissions,such as the ring current and near-Earth magnetotail.There is a special design in front of the detector,i.e.,a coded mask,with which an enhancement of spatial resolution from 2.5°to 0.5°is claimed.To quantitatively evaluate the reconstructed image after the coded mask,this paper first presents the simulations of ENA flux and count rates at storm-time levels,reconstructs the image afterward,and finally provides a detailed analysis of the reconstructed image by introducing five evaluation criteria.According to the results,the recommended exposure time to do the reconstruction is 1 min for ring current studies,and 10 min for the magnetotail and magnetopause studies.A free parameter during the reconstruction calculation,i.e.,the number of iterations,is set to 6.In this case,the locations of magnetospheric structures can be determined with an accuracy better than~0.5°and ENA counts can be reconstructed with a deviation less than~30%.Nevertheless,it is also noted that the estimation of expected counts detected by GENA in this paper is based on certain assumptions,making it an upper limit of the detected counts.Possible post-flight calibration may improve the estimation and provide an understanding of the instrument closer to reality.展开更多
Alkaline-earth-like(AEL)atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing.Typical AEL ground states possess no hyperfine splitting,but unfortunately a GH...Alkaline-earth-like(AEL)atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing.Typical AEL ground states possess no hyperfine splitting,but unfortunately a GHz-scale splitting seems necessary for Rydberg excitation.Though strong magnetic fields can induce a GHz-scale splitting,weak fields are desirable to avoid noise in experiments.Here,we provide two solutions to this outstanding challenge with realistic data of well-studied AEL isotopes.In the first theory,the two nuclear spin qubit states∣0〉and∣1〉are excited to Rydberg states∣r〉with detuningΔand 0,respectively,where a MHz-scale detuningΔarises from a weak magnetic field on the order of 1 G.With a proper ratio betweenΔandΩ,the qubit state∣1〉can be fully excited to the Rydberg state while∣0〉remains there.In the second theory,we show that by choosing appropriate intermediate states a two-photon Rydberg excitation can proceed with only one nuclear spin qubit state.The second theory is applicable whatever the magnitude of the magnetic field is.These theories bring a versatile means for quantum computation by combining the broad applicability of Rydberg blockade and the incomparable advantages of nuclear-spin quantum memory in two-electron neutral atoms.展开更多
A method is presented for retrieving the magnetospheric ion distribution from En-ergetic Neutral Atom (ENA) measurements made by the NUADU instrument on the TC-2 spacecraft. Based on the already well-established metho...A method is presented for retrieving the magnetospheric ion distribution from En-ergetic Neutral Atom (ENA) measurements made by the NUADU instrument on the TC-2 spacecraft. Based on the already well-established method of constrained lin-ear inversion, an iterance technique suitable for the low count ENA measurements has been developed which is tolerant of the noise background. By the iterance technique, it is possible for the first time to simultaneously retrieve the magneto-spheric ion distribution and the exospheric neutral density, and further to recover global ENA emissions in three dimensions. The technique is applied to a repre-sentative ENA image recorded in energy channel 2 (protons: 50―81 keV) of the NUADU instrument during a major geomagnetic storm and it is, thereby, shown that the retrieval method developed provides a useful tool for extracting ion distribution information from ENA data.展开更多
Mercury is a promising candidate for the optical lattice clock, due to its low sensitivity to the blackbody radiation. We develop a single folded beam magneto-optical trap for the neutral mercury optical lattice clock...Mercury is a promising candidate for the optical lattice clock, due to its low sensitivity to the blackbody radiation. We develop a single folded beam magneto-optical trap for the neutral mercury optical lattice clock, with a 253. 7nm frequency quadrupled laser. Up to 1.7 × 10^6 （202Hg） or 1.5 × 10^6 （199Hg） atoms can be captured, and the atom temperature is lowered to 170μK （202Hg） or 50μK （199Hg）. The cold atom signals of all six rich abundant isotopes are observed in this system.展开更多
Due to its low sensitivity to blackbody radiation, neutral mercury is a good candidate for the most accurate optical lattice clock. Here we report the observation of cold mercury atoms in a magneto-optical trap （MOT...Due to its low sensitivity to blackbody radiation, neutral mercury is a good candidate for the most accurate optical lattice clock. Here we report the observation of cold mercury atoms in a magneto-optical trap （MOT）. Because of the high vapor pressure at room temperature, the mercury source and the cold pump were cooled down to 40℃ and 70 ℃, respectively, to keep the science chamber in an ultra-high vacuum of 6×10^-9 Pa. Limited by the power of the UV cooling laser, the one beam folded MOT configuration was adopted, and 1.5×10^5 Hg-202 atoms were observed by fluorescence detection.展开更多
The main objective of the Mars Ion and Neutral Particle Analyzer(MINPA)aboard the Chinese Mars Exploration Mission(Tianwen-1)is to study the solar wind-Mars interaction by measuring the ions and energetic neutral atom...The main objective of the Mars Ion and Neutral Particle Analyzer(MINPA)aboard the Chinese Mars Exploration Mission(Tianwen-1)is to study the solar wind-Mars interaction by measuring the ions and energetic neutral atoms(ENAs)near Mars.The MINPA integrates ion and ENA measurements into one sensor head,sharing the same electronics box.The MINPA utilizes a standard toroidal top-hat electrostatic analyzer(ESA)followed by a time of flight(TOF)unit to provide measurement of ions with energies from 2.8 eV to 25.9 keV and ENAs from 50 eV to 3 keV with a base time resolution of 4 seconds.Highly polished silicon single crystal substrates with an Al2O3 film coating are used to ionize the ENAs into positive ions.These ions can then be analyzed by the ESA and TOF,to determine the energy and masses of the ENAs.The MINPA provides a 360°×90°field of view(FOV)with 22.5°×5.4°angular resolution for ion measurement,and a 360°×9.7°FOV with 22.5°×9.7°angular resolution for ENA measurement.The TOF unit combines a-15 kV acceleration high voltage with ultra-thin carbon foils to resolve H+,He2+,He+,O+,O2+and CO2+for ion measurement and to resolve H and O(≥16 amu group)for ENA measurement.Here we present the design principle and describe our ground calibration of the MINPA.展开更多
We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calcu...We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional （2D） quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal length of the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires.展开更多
We show that it is possible to localize a three-level cascade atom under the resonance condition when it passes through a standing-wave field. The localization peaks appear at the nodes of the standing-wave field, the...We show that it is possible to localize a three-level cascade atom under the resonance condition when it passes through a standing-wave field. The localization peaks appear at the nodes of the standing-wave field, the detecting probability is 50% in the subwavelength domain, and the peaks are narrower on the resonance than the off- resonance. The absorption is the same as that in the usual two-level medium at the nodes and is greatly suppressed outside the nodes due to the Autler-Townes splitting. This is in sharp contrast to the lambda scheme, in which the localization is impossible under the same resonance condition due to the depletion of population of the initial state by the probe field at the nodes and the electromagnetically induced transparency outside the nodes.展开更多
The quantum swap gate is one of the most useful gates for quantum computation. Two-qubit entanglement and a controlled-NOT quantum gate in a neutral Rydberg atom system have been achieved in recent experiments. It is ...The quantum swap gate is one of the most useful gates for quantum computation. Two-qubit entanglement and a controlled-NOT quantum gate in a neutral Rydberg atom system have been achieved in recent experiments. It is therefore very interesting to propose a scheme here for swapping a quantum state between two trapped neutral atoms via the Rydberg blockade mechanism. The atoms interact with a sequence of laser pulses without individual addressing. The errors of the swap gate due to imprecision of pulse length, finite Rydberg interaction, and atomic spontaneous emission are discussed.展开更多
Energetic neutral atoms(ENAs)are produced by the neutralization of energetic ions formed by shock-accelerated gradual solar energetic particle events(SEP).These high-energy ENAs(HENAs)can reach the Earth earlier than ...Energetic neutral atoms(ENAs)are produced by the neutralization of energetic ions formed by shock-accelerated gradual solar energetic particle events(SEP).These high-energy ENAs(HENAs)can reach the Earth earlier than the associated SEPs and thus can provide information about the SEPs at the lower corona.The HENA properties observed at Earth depend on the properties of the coronal mass ejection(CME)-driven shocks that accelerate the SEPs.Using a model of HENA production in a shock-accelerated SEP event,we semi-quantitatively investigate the energy-time spectrum of HENAs depending on the width,propagation speed,and direction of the shock,as well as the density and ion abundances of the lower corona.Compared to the baseline model parameters,the cases with a wider shock width angle or a higher coronal density would increase the HENA flux observed at the Earth,while the case with an Earthpropagating shock shows a softened HENA spectrum.The comparison of expected HENA fluxes in different cases with a flight-proven ENA instrument suggests that solar HENAs can feasibly be monitored with current technologies,which could provide a lead time of 2−3 hours for SEPs at a few MeV.We propose that monitoring of solar HENAs could provide a new method to forecast shock-driven SEP events that are capable of significant space weather impacts on the near-Earth environment.展开更多
A cold atom source is important for quantum metrology and precision measurement.To reduce the quantum projection noise limit in optical lattice clock,one can increase the number of cold atoms and reduce the dead time ...A cold atom source is important for quantum metrology and precision measurement.To reduce the quantum projection noise limit in optical lattice clock,one can increase the number of cold atoms and reduce the dead time by enhancing the loading rate.In this work,we realize an enhanced cold mercury atom source based on a two-dimensional(2D)magnetooptical trap(MOT).The vacuum system is composed of two titanium chambers connected with a differential pumping tube.Two stable cooling laser systems are adopted for the 2D-MOT and the three-dimensional(3D)-MOT,respectively.Using an optimized 2D-MOT and push beam,about 1.3×10^(6)atoms,which are almost an order of magnitude higher than using a pure 3D-MOT,are loaded into the 3D-MOT for202Hg atoms.This enhanced cold mercury atom source is helpful in increasing the frequency stability of a neutral mercury lattice clock.展开更多
A new bipartition neutral transport model has been developed for simulation of the hydrogenic neutral particle transport in the vicinity of HL-2A divertor target plate.The numerical calculation results on the basis of...A new bipartition neutral transport model has been developed for simulation of the hydrogenic neutral particle transport in the vicinity of HL-2A divertor target plate.The numerical calculation results on the basis of this model are fairly consistent with the results obtained with the "multi-generation method". One possible application of this model is to provide a source term originating from neutral transport calculation for any other edge plasma transport code, for instance, B-2 code, which has been used to simulate edge plasma transport of the HL-2A divertor configuration. Especially it can be utilized to quickly classify the plasma in divertor region as high or low recycling regime.展开更多
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 National Key Research and Development Program of China (Grant No.2021YFA1402002)the Innovation Program for Quantum Science and Technology (Grant No.2023ZD0300400)the National Natural Science Foundation of China (Grant Nos.U21A6006,U21A20433,92465201,12474360,and 92265108)。
文摘The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.
基金Supported by the National Natural Science Foundation of China under Grant No.10974028 the Doctoral Foundation of the Ministry of Education of China under Grant No.20093514110009+1 种基金 the Natural Science Foundation of Fujian Province under Grant No.2009J06002Funds from the State Key Laboratory Breeding Base of Photocatalysis,Fuzhou University
文摘We propose a scheme for realizing a controlled geometric phase gate for two neutral atoms.We apply thestimulated Raman adiabatic passage to transfer atoms from their ground states into Rydberg excited states, and use theRydberg interaction induced energy shifts to generate geometric phase and construct quantum gates.
文摘Violent galactic encounters or mergers are the leading contenders for triggering luminous quasar activity at low redshifts: such interactions can lead to the concentration of gas in the host galactic nucleus, thus fueling the suspected central superrmassive black hole. Although optical images show a number of violently interacting systems, in many cases the evidence for such interactions is only circumstantial (e.g., asymmetric optical morphologies, projected nearby companion galaxies) or not at all apparent. Here we image quasar host galaxies for the first time in the redshifted 21 cm line emission of neutral atomic hydrogen (HI) gas, which in nearby galaxies has proven to be a particularly sensitive as well as enduring tracer of tidal interactions. The three quasars studied have different optical environments normally seen around low reshift quasars, ranging from a perhaps mildly interacting system to a relatively undisturbed host with a projected neighbouring galaxy to an isolated and apparently serene host galaxy. By contrast with their optical appearences, all three quasar host galaxies exhibit ongoing or remnant tidal HI disruptions tracing galactic encounters or mergers. These observations provide a better understanding of the likely stage of their interaction.
基金supported by the BK21 Plus program through the National Research Foundation(NRF)funded by the Ministry of Education of Korea.
文摘Vast magnetospheric regions are mapped along the field lines to the narrow latitudinal band of the polar/auroral regions. Therefore monitoring of solar wind energy dissipation into the ionosphere at auroral latitudes gives unique opportunities to study geomagnetic disturbances in their complexity from a relatively well-localized vantage point. Here we introduce and present the current state of a recently proposed science project for coordinated monitoring of high-latitude activity with the EISCAT (European Incoherent Scatter) radar array supported by ground-based magnetometer and optical data and ENA (Energetic Neutral Atom) observation from the CINEMA (Cube-Sat for Ions, Neutrals, Electrons and Magnetic field) satellite system.
文摘The spectrum and the wave function of neutral atoms in the magnetic field of a Kepler guide are presented by reducing a two dimensional stationary Schrdinger equation to a one dimensional hydrogen atom in Rydberg states. In addition, we set the scale for the atomic orbits and binding energy in the quantum regime, and compare it with the outcome of the experiment. At the same time, we find that reducing the current and radius of the wire properly will increase the loading efficiency of the Kepler guide.
基金supported by the National Natural Science Foundation of China(Grant Nos.42322408,42188108,42441809)the Climbing Program of National Space Science Center,Chinese Academy of Sciences(Grant Nos.E4PD3005,E4PD40015S)。
文摘The grid-based energetic neutral atom imager(GENA)onboard the Queqiao-2 satellite is designed to capture high spatiotemporal resolution data of the Earth's ring current from a lunar orbit at a distance of 380000 km.The instrument operates based on the time-of-flight(TOF)method and the grid-based encoding modulation principle.Key specifications of GENA include the following:detection of H atoms with an energy range of 4–200 keV,detection of O atoms with an energy range of 8–250 ke V,an energy resolution of better than 1 keV@10 keV,a field of view(FOV)of 19.72°×45.07°,an angular resolution of 0.43°,and a geometric factor of 19.2 cm^(2)sr.This paper presents some ground calibration results obtained during the testing of the proposed imager.GENA is expected to perform energetic neutral atom imaging of the Earth's magnetosphere and provide crucial data for studying particle injection from the magnetotail into the ring current region,as well as the generation and evolution of geomagnetic storms.
文摘Coded aperture imaging(CAI)is widely used as an energetic-particles telescope in high-energy astrophysics.A typical CAI system consists of a coded mask(CM),a position-sensitive detector,and reconstruction algorithms that recover the source distributions from the measured projections.The imaging performance of CAI largely depends on the CM design,which governs the field-of-view(FOV),spatial resolution,sensitivity,and signalto-noise ratio(SNR).
基金supported by the National Natural Science Foundation of China(Grant Nos.42188101,42322408)the Climbing Program of National Space Science Center(Grant No.E4PD3005)。
文摘The imaging of terrestrial energetic neutral atoms(ENAs)is potentially a powerful way to reveal the large-scale characteristics and overall evolutions of the magnetosphere.The grid-based ENA(GENA)detector onboard Queqiao-2 aims at providing global images of the main regions of ENA emissions,such as the ring current and near-Earth magnetotail.There is a special design in front of the detector,i.e.,a coded mask,with which an enhancement of spatial resolution from 2.5°to 0.5°is claimed.To quantitatively evaluate the reconstructed image after the coded mask,this paper first presents the simulations of ENA flux and count rates at storm-time levels,reconstructs the image afterward,and finally provides a detailed analysis of the reconstructed image by introducing five evaluation criteria.According to the results,the recommended exposure time to do the reconstruction is 1 min for ring current studies,and 10 min for the magnetotail and magnetopause studies.A free parameter during the reconstruction calculation,i.e.,the number of iterations,is set to 6.In this case,the locations of magnetospheric structures can be determined with an accuracy better than~0.5°and ENA counts can be reconstructed with a deviation less than~30%.Nevertheless,it is also noted that the estimation of expected counts detected by GENA in this paper is based on certain assumptions,making it an upper limit of the detected counts.Possible post-flight calibration may improve the estimation and provide an understanding of the instrument closer to reality.
文摘Alkaline-earth-like(AEL)atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing.Typical AEL ground states possess no hyperfine splitting,but unfortunately a GHz-scale splitting seems necessary for Rydberg excitation.Though strong magnetic fields can induce a GHz-scale splitting,weak fields are desirable to avoid noise in experiments.Here,we provide two solutions to this outstanding challenge with realistic data of well-studied AEL isotopes.In the first theory,the two nuclear spin qubit states∣0〉and∣1〉are excited to Rydberg states∣r〉with detuningΔand 0,respectively,where a MHz-scale detuningΔarises from a weak magnetic field on the order of 1 G.With a proper ratio betweenΔandΩ,the qubit state∣1〉can be fully excited to the Rydberg state while∣0〉remains there.In the second theory,we show that by choosing appropriate intermediate states a two-photon Rydberg excitation can proceed with only one nuclear spin qubit state.The second theory is applicable whatever the magnitude of the magnetic field is.These theories bring a versatile means for quantum computation by combining the broad applicability of Rydberg blockade and the incomparable advantages of nuclear-spin quantum memory in two-electron neutral atoms.
基金the National Natural Science Foundation of China (Grant No. 40674083)Chinese National Key Laboratory research outlay (Grant No. 40523006)SMcKL acknowledges with appreciation the support of Enterprise Ireland
文摘A method is presented for retrieving the magnetospheric ion distribution from En-ergetic Neutral Atom (ENA) measurements made by the NUADU instrument on the TC-2 spacecraft. Based on the already well-established method of constrained lin-ear inversion, an iterance technique suitable for the low count ENA measurements has been developed which is tolerant of the noise background. By the iterance technique, it is possible for the first time to simultaneously retrieve the magneto-spheric ion distribution and the exospheric neutral density, and further to recover global ENA emissions in three dimensions. The technique is applied to a repre-sentative ENA image recorded in energy channel 2 (protons: 50―81 keV) of the NUADU instrument during a major geomagnetic storm and it is, thereby, shown that the retrieval method developed provides a useful tool for extracting ion distribution information from ENA data.
基金Supported by the National Natural Science Foundation of China under Grant No 91436105the National Basic Research Program of China under Grant No 2011CB921504the Research Project of Shanghai Science and Technology Commission under Grant No 09DJ1400700
文摘Mercury is a promising candidate for the optical lattice clock, due to its low sensitivity to the blackbody radiation. We develop a single folded beam magneto-optical trap for the neutral mercury optical lattice clock, with a 253. 7nm frequency quadrupled laser. Up to 1.7 × 10^6 （202Hg） or 1.5 × 10^6 （199Hg） atoms can be captured, and the atom temperature is lowered to 170μK （202Hg） or 50μK （199Hg）. The cold atom signals of all six rich abundant isotopes are observed in this system.
基金Project supported by the Research Project of Shanghai Science and Technology Commission, China (Grant No. 09DJ1400700)the National Natural Science Foundation of China (Grant Nos. 10974211 and 11104292)the National Basic Research Program of China (Grant No. 2011CB921504)
文摘Due to its low sensitivity to blackbody radiation, neutral mercury is a good candidate for the most accurate optical lattice clock. Here we report the observation of cold mercury atoms in a magneto-optical trap （MOT）. Because of the high vapor pressure at room temperature, the mercury source and the cold pump were cooled down to 40℃ and 70 ℃, respectively, to keep the science chamber in an ultra-high vacuum of 6×10^-9 Pa. Limited by the power of the UV cooling laser, the one beam folded MOT configuration was adopted, and 1.5×10^5 Hg-202 atoms were observed by fluorescence detection.
基金funded by the Chinese National Space Administration.
文摘The main objective of the Mars Ion and Neutral Particle Analyzer(MINPA)aboard the Chinese Mars Exploration Mission(Tianwen-1)is to study the solar wind-Mars interaction by measuring the ions and energetic neutral atoms(ENAs)near Mars.The MINPA integrates ion and ENA measurements into one sensor head,sharing the same electronics box.The MINPA utilizes a standard toroidal top-hat electrostatic analyzer(ESA)followed by a time of flight(TOF)unit to provide measurement of ions with energies from 2.8 eV to 25.9 keV and ENAs from 50 eV to 3 keV with a base time resolution of 4 seconds.Highly polished silicon single crystal substrates with an Al2O3 film coating are used to ionize the ENAs into positive ions.These ions can then be analyzed by the ESA and TOF,to determine the energy and masses of the ENAs.The MINPA provides a 360°×90°field of view(FOV)with 22.5°×5.4°angular resolution for ion measurement,and a 360°×9.7°FOV with 22.5°×9.7°angular resolution for ENA measurement.The TOF unit combines a-15 kV acceleration high voltage with ultra-thin carbon foils to resolve H+,He2+,He+,O+,O2+and CO2+for ion measurement and to resolve H and O(≥16 amu group)for ENA measurement.Here we present the design principle and describe our ground calibration of the MINPA.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10174050, 10374029, and 10434060, the Shanghai Priority Academic Discipline, and the 211 Foundation of the Ministry of Education of China.
文摘We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional （2D） quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal length of the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires.
基金Supported by the National Natural Science Foundation of China under Grant No 10574052.
文摘We show that it is possible to localize a three-level cascade atom under the resonance condition when it passes through a standing-wave field. The localization peaks appear at the nodes of the standing-wave field, the detecting probability is 50% in the subwavelength domain, and the peaks are narrower on the resonance than the off- resonance. The absorption is the same as that in the usual two-level medium at the nodes and is greatly suppressed outside the nodes due to the Autler-Townes splitting. This is in sharp contrast to the lambda scheme, in which the localization is impossible under the same resonance condition due to the depletion of population of the initial state by the probe field at the nodes and the electromagnetically induced transparency outside the nodes.
基金supported by the National Natural Science Foundation of China (Grant No. 10974028)the Doctoral Foundation of the Ministry of Education of China (Grant No. 20093514110009)+3 种基金the Natural Science Foundation of Fujian Province of China (Grant No. 2009J06002)the Fund from Fuzhou University (Grant No. 022408)the National Basic Research Program of China (Grant Nos. 2011CB921200 and 2011CBA00200)the China Postdoctoral Science Foundation (Grant No. 20110490828)
文摘The quantum swap gate is one of the most useful gates for quantum computation. Two-qubit entanglement and a controlled-NOT quantum gate in a neutral Rydberg atom system have been achieved in recent experiments. It is therefore very interesting to propose a scheme here for swapping a quantum state between two trapped neutral atoms via the Rydberg blockade mechanism. The atoms interact with a sequence of laser pulses without individual addressing. The errors of the swap gate due to imprecision of pulse length, finite Rydberg interaction, and atomic spontaneous emission are discussed.
文摘Energetic neutral atoms(ENAs)are produced by the neutralization of energetic ions formed by shock-accelerated gradual solar energetic particle events(SEP).These high-energy ENAs(HENAs)can reach the Earth earlier than the associated SEPs and thus can provide information about the SEPs at the lower corona.The HENA properties observed at Earth depend on the properties of the coronal mass ejection(CME)-driven shocks that accelerate the SEPs.Using a model of HENA production in a shock-accelerated SEP event,we semi-quantitatively investigate the energy-time spectrum of HENAs depending on the width,propagation speed,and direction of the shock,as well as the density and ion abundances of the lower corona.Compared to the baseline model parameters,the cases with a wider shock width angle or a higher coronal density would increase the HENA flux observed at the Earth,while the case with an Earthpropagating shock shows a softened HENA spectrum.The comparison of expected HENA fluxes in different cases with a flight-proven ENA instrument suggests that solar HENAs can feasibly be monitored with current technologies,which could provide a lead time of 2−3 hours for SEPs at a few MeV.We propose that monitoring of solar HENAs could provide a new method to forecast shock-driven SEP events that are capable of significant space weather impacts on the near-Earth environment.
文摘A cold atom source is important for quantum metrology and precision measurement.To reduce the quantum projection noise limit in optical lattice clock,one can increase the number of cold atoms and reduce the dead time by enhancing the loading rate.In this work,we realize an enhanced cold mercury atom source based on a two-dimensional(2D)magnetooptical trap(MOT).The vacuum system is composed of two titanium chambers connected with a differential pumping tube.Two stable cooling laser systems are adopted for the 2D-MOT and the three-dimensional(3D)-MOT,respectively.Using an optimized 2D-MOT and push beam,about 1.3×10^(6)atoms,which are almost an order of magnitude higher than using a pure 3D-MOT,are loaded into the 3D-MOT for202Hg atoms.This enhanced cold mercury atom source is helpful in increasing the frequency stability of a neutral mercury lattice clock.
文摘A new bipartition neutral transport model has been developed for simulation of the hydrogenic neutral particle transport in the vicinity of HL-2A divertor target plate.The numerical calculation results on the basis of this model are fairly consistent with the results obtained with the "multi-generation method". One possible application of this model is to provide a source term originating from neutral transport calculation for any other edge plasma transport code, for instance, B-2 code, which has been used to simulate edge plasma transport of the HL-2A divertor configuration. Especially it can be utilized to quickly classify the plasma in divertor region as high or low recycling regime.
