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
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
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 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 st...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
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 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
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
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 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 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.
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.
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.
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.
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.
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.
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 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.
