Interactions between atoms in ultracold quantum gases play an important role in the study of the quantum simulation of many-body physics.Feshbach resonance is a versatile tool to control atomic interactions,where the ...Interactions between atoms in ultracold quantum gases play an important role in the study of the quantum simulation of many-body physics.Feshbach resonance is a versatile tool to control atomic interactions,where the atom-loss spectra are widely used to characterize Feshbach resonances of various atomic species.Here,we report the experimental observation of momentum-induced broadening of widths in atom-loss spectra of narrow ^(133)Cs Feshbach resonances.We drive Bragg excitation to kick the Bose-Einstein condensate of Cs atoms in a cigar-shaped optical trap,and measure the atom-loss spectra of narrow Feshbach resonances of moving ultracold atoms near the magnetic fields 19.84 G and 47.97 G.We show that the widths of the atom-loss spectra are broadened for the atoms with the momenta of 2hk,and 4hk,and even observe splitting in the Feshbach resonance of the atoms with momentum 4hk.Our work may open the way for exploring the interesting physical phenomena arising from the collective velocity of colliding atoms that have been ignored in general.展开更多
Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a l...Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a laboratory laser-induced breakdown spectroscopy （LIBS） apparatus mainly comprising a sealed optical module and an analysis chamber has been designed for possible application in cement plants for on-site quality analysis of cement. Emphasis is placed on the structure and operation of the LIBS apparatus, the sealed optical path, the temperature controlled spectrometer, the sample holder, the proper calibration model established for minimizing the matrix effects, and a correction method proposed for overcoming the ＇drift＇ obstacle. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The absolute measurement errors presented here for oxides analysis are within 0.5%, while those of ratio values are in the range of 0.02 to 0.05. According to the obtained results, this laboratory LIBS apparatus is capable of performing reliable and accurate, composition and proximate analysis of cement and is suitable for application in cement plants.展开更多
We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Tw...We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Two factors that result in the excess noises of the quantum key distribution system are analyzed.The first is the relative phase dithering between the signal and local fields,and the second is the local field leakage into the signal field due to the scattering process that depolarizes the local field.It is found that the latter has a significant impact on the excess noise,which is the main limiting factor to the long-distance secure quantum transmission.Some protocols are also given to decrease the excess noise effectively.展开更多
This paper reports that ultracold atoms are populated into different nS and nD Rydberg states （n=25-52） by two-photon excitation. The ionization spectrum of an ultracold Rydberg atom is acquired in a cesium magneto-...This paper reports that ultracold atoms are populated into different nS and nD Rydberg states （n=25-52） by two-photon excitation. The ionization spectrum of an ultracold Rydberg atom is acquired in a cesium magneto-optical trap by using the method of pulse field ionization. This denotes nS and nD states in the ionization spectrum and fits the data of energy levels of different Rydberg states to obtain quantum defects of nS and nD states.展开更多
A symmetric two-mode Gaussian entangled state is used to investigate the effect of excess noise on entanglement sudden death and Gaussian quantum discord with continuous variables. The results show that the excess noi...A symmetric two-mode Gaussian entangled state is used to investigate the effect of excess noise on entanglement sudden death and Gaussian quantum discord with continuous variables. The results show that the excess noise in the channel can lead to entanglement sudden death of a symmetric two-mode Gaussian entangled state, while Gaussian quantum discord never vanishes. As a practical application, the security of a quantum key distribution （QKD） scheme based on a symmetric two-mode Gaussian entangled state against collective Gaussian attacks is analyzed. The calculation results show that the secret key cannot be distilled when entanglement vanishes and only quantum discord exists in such a QKD scheme.展开更多
This paper has investigated quantum teleportation of even and odd coherent states in terms of the EPR entanglement states for continuous variables. It discusses the relationship between the fidelity and the entangleme...This paper has investigated quantum teleportation of even and odd coherent states in terms of the EPR entanglement states for continuous variables. It discusses the relationship between the fidelity and the entanglement of EPR states, which is characterized by the degree of squeezing and the gain of classical channels. It shows that the quality of teleporting quantum states also depends on the characteristics of the states themselves. The properties of teleporting even and odd coherent states at different intensities are investigated. The difference of teleporting two such kinds of quantum states are analysed based on the quantum distance function.展开更多
Electronic charge of molecules can move on time scales when the nuclei stand practically still,from few hundreds of attoseconds to few femtoseconds.This ultrafast process is called“charge migration”.A typical conseq...Electronic charge of molecules can move on time scales when the nuclei stand practically still,from few hundreds of attoseconds to few femtoseconds.This ultrafast process is called“charge migration”.A typical consequence is rapid change of electronic dipole,which points to the center of charge.Corresponding linear(one-dimensional,1D)and planar(2D)dipolar motions have already been well documented.Here we construct the first case of charge migration which causes chiral 3D dipolar motion,specifically along a helix about oriented iodo-acetylene(HCCI).Quantum dynamics simulations show that this can be induced by well-designed laser pulses.展开更多
We report on the attainment of quantum degeneracy of 40^K by means of efficient thermal collisions with the evaporatively cooled 87^Rb atoms. In a quadrupole-Ioffe configuration trap, potassium atoms axe cooled to 0.5...We report on the attainment of quantum degeneracy of 40^K by means of efficient thermal collisions with the evaporatively cooled 87^Rb atoms. In a quadrupole-Ioffe configuration trap, potassium atoms axe cooled to 0.5 times the Fermi temperature. We obtain up to 7.59 × 10^5 degenerate fermions 40^K.展开更多
The fidelity of quantum teleportation of a single-mode squeezed state of light is calculated based on the general theory of quantum-mechanical measurement in the Schrodinger picture. It is shown that the criterion for...The fidelity of quantum teleportation of a single-mode squeezed state of light is calculated based on the general theory of quantum-mechanical measurement in the Schrodinger picture. It is shown that the criterion for the nonclassical state teleportation is different from that for coherent state. F = 1/2 is no longer the rigorous boundary between classical and quantum teleportation for a squeezed state of light. When the quantum entanglement of an Einstein-Podolsky-Rosen （EPR） beam used for teleportation and the parameters of the system are given, the fidelity depends on the squeezing of the input squeezed state. The higher the squeezing is, the smaller the fidelity is, and the lower the classical limitation of fidelity is. The dependence of the optimum gain for teleporting a squeezed vacuum state upon the EPR entanglement is also calculated. The results obtained provide important references for designing experimental systems of teleporting a non-classical state and judging the quality of the teleported quantum state.展开更多
We study the dynamics of geometric quantum discord(GQD) between two qubits,each qubit interacting at the same time with K independent multiple bosonic reservoirs at zero temperature.In both weak and strong qubit-reser...We study the dynamics of geometric quantum discord(GQD) between two qubits,each qubit interacting at the same time with K independent multiple bosonic reservoirs at zero temperature.In both weak and strong qubit-reservoirs coupling regimes,we find that the increase of the number K of reservoirs can induce the damped oscillation of GQD,and enhance the memory effects of the overall environment.And the Hilbert-Schmidt norm GQD(two-norm GQD) is always smaller than the trace norm geometric quantum discord(one-norm GQD).Therefore,the one-norm GQD is a better way to measure the quantum correlation.Finally,we propose an effective strategy to improve GQD by using partially collapsing measurements,and we find that the protection effect is better with the increase of the weak measurement strength.展开更多
In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-...In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-free frequency conversion of a quantum state can be achieved by injecting a strong signal field. The dependences of conversion efficiency on the pump parameter, extra losses and input state amplitude are also analysed.展开更多
The output amplitude noises of one squeezed probe light which is at resonance throughout different optical depths media in strong- and weak-coupling-field regimes are investigated theoretically.By comparing the output...The output amplitude noises of one squeezed probe light which is at resonance throughout different optical depths media in strong- and weak-coupling-field regimes are investigated theoretically.By comparing the output quantum noises for different Rabi frequencies of coupling field and also for different optical depths,it is found that the optimal squeezing preservation of the probe light occurs in an optically thin medium with strong-coupling-field,where we can obtain the output squeezing close to the input one at nonzero detection frequency.展开更多
Non-Hermitian systems have observed numerous novel phenomena and might lead to various applications.Unlike standard quantum physics,the conservation of energy guaranteed by the closed system is broken in the non-Hermi...Non-Hermitian systems have observed numerous novel phenomena and might lead to various applications.Unlike standard quantum physics,the conservation of energy guaranteed by the closed system is broken in the non-Hermitian system,and the energy can be exchanged between the system and the environment.Here we present a scheme for simulating the dissipative phase transition with an open quantum optical system.The competition between the coherent interaction and dissipation leads to the second-order phase transition.Furthermore,the quantum correlation in terms of squeezing is studied around the critical point.Our work may provide a new route to explore the non-Hermitian quantum physics with feasible techniques in experiments.展开更多
We present a protocol to realize topological discrete-time quantum walks,which comprise a sequence of spindependent flipping displacement operations and quantum coin tossing operations,with a single trapped ion.It is ...We present a protocol to realize topological discrete-time quantum walks,which comprise a sequence of spindependent flipping displacement operations and quantum coin tossing operations,with a single trapped ion.It is demonstrated that the information of bulk topological invariants can be extracted by measuring the average projective phonon number when the walk takes place in coherent state space.Interestingly,the specific chiral symmetry owned by our discrete-time quantum walks simplifies the measuring process.Furthermore,we prove the robustness of such bulk topological invariants by introducing dynamical disorder and decoherence.Our work provides a simple method to measure bulk topological features in discrete-time quantum walks,which can be experimentally realized in the system of single trapped ions.展开更多
This paper describes the generation and observation of sub-Poissonian light in an open-loop system with low quantum efficiency at room temperature.The experimental results show that the photocurrent Huctuation spectru...This paper describes the generation and observation of sub-Poissonian light in an open-loop system with low quantum efficiency at room temperature.The experimental results show that the photocurrent Huctuation spectrum density can be reduced below the shot noise limit by 72%(-5.5 dB)in an open-loop light-emitting diode(LED)system at the frequency of 2MHz.The noise reduction is not limited by quantum efficiency of the LEDr or the current transfer efficiency.展开更多
We propose a scheme for the simultaneously preparation radiation-field modes of a single photon and a superposition of zero- and one-photon states, based on the coherent quantum state displacement and photon subtracti...We propose a scheme for the simultaneously preparation radiation-field modes of a single photon and a superposition of zero- and one-photon states, based on the coherent quantum state displacement and photon subtraction from two-mode squeezed state. It is shown that the single-photon and the superposition states can be obtained by only choosing the suitable parameter of displacements. The experimental feasibility to accomplish this scheme is also discussed.展开更多
We report a compact experimental setup for producing a quantum degenerate mixture of Bose23Na and Fermi40K gases. The atoms are collected in dual dark magneto–optical traps(MOT) with species timesharing loading to re...We report a compact experimental setup for producing a quantum degenerate mixture of Bose23Na and Fermi40K gases. The atoms are collected in dual dark magneto–optical traps(MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D2line for23Na and D1line for40K. The microwave evaporation cooling is used to cool23Na in |F = 2, mF= 2〉 in an optically plugged magnetic trap, meanwhile,40K in |F = 9/2, mF= 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where23Na atoms are immediately transferred to |1, 1〉 for further effective cooling to avoid the strong three-body loss between23Na atoms in |2, 2〉 and40K atoms in |9/2, 9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of40K with 1.9 × 10^(5) atoms at T/TF= 0.5 in the |9/2, 9/2〉 hyperfine state coexists with a Bose–Einstein condensate(BEC) of23Na with 8 × 10^(4) atoms in the |1, 1〉 hyperfine state at 300 n K. We also can produce the two species mixture with the tunable population imbalance by adjusting the 23Na magneto–optical trap loading time.展开更多
We construct a one-dimensional quasiperiodic quantum walk to investigate the localization–delocalization transition.The inverse participation ratio and Lyapunov exponent are employed as two indexes to determine the m...We construct a one-dimensional quasiperiodic quantum walk to investigate the localization–delocalization transition.The inverse participation ratio and Lyapunov exponent are employed as two indexes to determine the mobility edge, a critical energy to distinguish the energy regions of extended and localized states. The analytical solution of mobility edge is obtained by the Lyapunov exponents in global theory, and the consistency of the two indexes is confirmed. We further study the dynamic characteristics of the quantum walk and show that the probabilities are localized to some specific lattice sites with time evolution. This phenomenon is explained by the effective potential of the Hamiltonian which corresponds to the phase in the coin operator of the quantum walk.展开更多
An optical-tweezers-based dual-frequency-band particle tracking system was designed and fabricated for liquid viscositydetection. On the basis of the liquid viscosity dependent model of the particle’s restricted Brow...An optical-tweezers-based dual-frequency-band particle tracking system was designed and fabricated for liquid viscositydetection. On the basis of the liquid viscosity dependent model of the particle’s restricted Brownian motion with theFax´en correction taken into account, the liquid viscosity and optical trap stiffness were determined by fitting the theoreticalprediction with the measured power spectral densities of the particle’s displacement and velocity that were derived from thedual-frequency-band particle tracking data. When the SiO2 beads were employed as probe particles in the measurements ofdifferent kinds of liquids, the measurement results exhibit a good agreement with the reported results, as well as a detectionuncertainty better than 4.6%. This kind of noninvasive economical technique can be applied in diverse environments forboth in situ and ex situ viscosity detection of liquids.展开更多
We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin st...We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the ODT.We observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical trap.By optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the ODT.We experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are obtained.The ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.展开更多
基金funded by the National Key Research and Development Program of China(Grant No.2022YFA1404201)the National Natural Science Foundation of China(Grant Nos.62020106014,92165106,62175140,12074234,and 11974331)the Applied Basic Research Project of Shanxi Province,China(Grant No.202203021224001)。
文摘Interactions between atoms in ultracold quantum gases play an important role in the study of the quantum simulation of many-body physics.Feshbach resonance is a versatile tool to control atomic interactions,where the atom-loss spectra are widely used to characterize Feshbach resonances of various atomic species.Here,we report the experimental observation of momentum-induced broadening of widths in atom-loss spectra of narrow ^(133)Cs Feshbach resonances.We drive Bragg excitation to kick the Bose-Einstein condensate of Cs atoms in a cigar-shaped optical trap,and measure the atom-loss spectra of narrow Feshbach resonances of moving ultracold atoms near the magnetic fields 19.84 G and 47.97 G.We show that the widths of the atom-loss spectra are broadened for the atoms with the momenta of 2hk,and 4hk,and even observe splitting in the Feshbach resonance of the atoms with momentum 4hk.Our work may open the way for exploring the interesting physical phenomena arising from the collective velocity of colliding atoms that have been ignored in general.
基金supported by National Natural Science Foundation of China(Nos.61127017,61378047,61205216,61178009,61108030,61475093,and 61275213)the National Key Technology R&D Program of China(No.2013BAC14B01)+2 种基金the 973 Program of China(No.2012CB921603)the Shanxi Natural Science Foundation,China(Nos.2013021004-1,2012021022-1)the Shanxi Scholarship Council of China(Nos.2013-011 and 2013-01)
文摘Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a laboratory laser-induced breakdown spectroscopy （LIBS） apparatus mainly comprising a sealed optical module and an analysis chamber has been designed for possible application in cement plants for on-site quality analysis of cement. Emphasis is placed on the structure and operation of the LIBS apparatus, the sealed optical path, the temperature controlled spectrometer, the sample holder, the proper calibration model established for minimizing the matrix effects, and a correction method proposed for overcoming the ＇drift＇ obstacle. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The absolute measurement errors presented here for oxides analysis are within 0.5%, while those of ratio values are in the range of 0.02 to 0.05. According to the obtained results, this laboratory LIBS apparatus is capable of performing reliable and accurate, composition and proximate analysis of cement and is suitable for application in cement plants.
基金Supported by the National Science Foundation of China(11074156)the TYAL,the National Basic Research Program of China(2010CB923101)+1 种基金the NSFC Project for Excellent Research Team(61121064)the Shanxi Scholarship Council of China.
文摘We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Two factors that result in the excess noises of the quantum key distribution system are analyzed.The first is the relative phase dithering between the signal and local fields,and the second is the local field leakage into the signal field due to the scattering process that depolarizes the local field.It is found that the latter has a significant impact on the excess noise,which is the main limiting factor to the long-distance secure quantum transmission.Some protocols are also given to decrease the excess noise effectively.
基金supported by the 973 Program of China(Grant No 2006CB921603)the National Natural Science Foundation of China (Grant Nos 10574084,60678003 and 60778008)+1 种基金the Special Foundation for State Major Basic Research Program of China(Grant No 2005CCA06300)the Scholarship Foundation of Shanxi Province,China
文摘This paper reports that ultracold atoms are populated into different nS and nD Rydberg states （n=25-52） by two-photon excitation. The ionization spectrum of an ultracold Rydberg atom is acquired in a cesium magneto-optical trap by using the method of pulse field ionization. This denotes nS and nD states in the ionization spectrum and fits the data of energy levels of different Rydberg states to obtain quantum defects of nS and nD states.
基金supported by the National Basic Research Program of China(Grant No.2010CB923103)the National Natural Science Foundation of China(GrantNos.11174188 and 61121064)the Fund from the Shanxi Scholarship Council of China(Grant No.2012-010)
文摘A symmetric two-mode Gaussian entangled state is used to investigate the effect of excess noise on entanglement sudden death and Gaussian quantum discord with continuous variables. The results show that the excess noise in the channel can lead to entanglement sudden death of a symmetric two-mode Gaussian entangled state, while Gaussian quantum discord never vanishes. As a practical application, the security of a quantum key distribution （QKD） scheme based on a symmetric two-mode Gaussian entangled state against collective Gaussian attacks is analyzed. The calculation results show that the secret key cannot be distilled when entanglement vanishes and only quantum discord exists in such a QKD scheme.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10434080, 10374062, 60578018）, NSFC-RFBR Joint Program, Research Funds for Returned Scholar Abroad from Shanxi Province and also supported by the CFKSTIP （Grant No 705010） and PCSIRT from Ministry of Education of China.
文摘This paper has investigated quantum teleportation of even and odd coherent states in terms of the EPR entanglement states for continuous variables. It discusses the relationship between the fidelity and the entanglement of EPR states, which is characterized by the degree of squeezing and the gain of classical channels. It shows that the quality of teleporting quantum states also depends on the characteristics of the states themselves. The properties of teleporting even and odd coherent states at different intensities are investigated. The difference of teleporting two such kinds of quantum states are analysed based on the quantum distance function.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0304203)the Program for Changjiang Scholars and Innovative Research Team(Grant No.IRT17R70)+4 种基金the National Natural Science Foundation of China(Grant Nos.12004193 and 11904215)the 111 Project(Grant No.D18001)the Fund for Shanxi 1331 Project Key Subjects Constructionthe Hundred Talent Program of Shanxi ProvinceNJUPT-SF(Grant No.NY220089)。
文摘Electronic charge of molecules can move on time scales when the nuclei stand practically still,from few hundreds of attoseconds to few femtoseconds.This ultrafast process is called“charge migration”.A typical consequence is rapid change of electronic dipole,which points to the center of charge.Corresponding linear(one-dimensional,1D)and planar(2D)dipolar motions have already been well documented.Here we construct the first case of charge migration which causes chiral 3D dipolar motion,specifically along a helix about oriented iodo-acetylene(HCCI).Quantum dynamics simulations show that this can be induced by well-designed laser pulses.
基金Supported in part by the National Basic Research Programme of China under Grant No 2006CB921101, the National Natural Science Foundation of China for Distinguished Young Scholars under Grant No 10725416, the National Natural Science Foundation of China under Grant No 60678029, the Programme for New Century Excellent Talents in University under Grant No NCET-04-0256, the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20050108007, the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China under Grant No 705010, the Programme for Changjiang Scholars and Innovative Research Team in University, the Natural Science Foundation of Shanxi Province under Grant No 2006011003, and the Research Fund for the Returned Abroad Scholars of Shanxi Province. The authors thank Professor Kunchi PENG and Professor Changde Xie for valuable advice and support. Jing Zhang thanks Junming Wang, Baolong Lu and Xiaoji Zhou for useful discussions, Professor Weiping Zhang and Professor Wuming Liu for good advice.
文摘We report on the attainment of quantum degeneracy of 40^K by means of efficient thermal collisions with the evaporatively cooled 87^Rb atoms. In a quadrupole-Ioffe configuration trap, potassium atoms axe cooled to 0.5 times the Fermi temperature. We obtain up to 7.59 × 10^5 degenerate fermions 40^K.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60278010, 60238010, and 60478808, the Shanxi Natural Science Foundation under Grant No 20041039, and the Returned Scholar Foundation.
文摘The fidelity of quantum teleportation of a single-mode squeezed state of light is calculated based on the general theory of quantum-mechanical measurement in the Schrodinger picture. It is shown that the criterion for the nonclassical state teleportation is different from that for coherent state. F = 1/2 is no longer the rigorous boundary between classical and quantum teleportation for a squeezed state of light. When the quantum entanglement of an Einstein-Podolsky-Rosen （EPR） beam used for teleportation and the parameters of the system are given, the fidelity depends on the squeezing of the input squeezed state. The higher the squeezing is, the smaller the fidelity is, and the lower the classical limitation of fidelity is. The dependence of the optimum gain for teleporting a squeezed vacuum state upon the EPR entanglement is also calculated. The results obtained provide important references for designing experimental systems of teleporting a non-classical state and judging the quality of the teleported quantum state.
基金Project supported by the National Natural Science Foundation of China(Grant No.11772177)。
文摘We study the dynamics of geometric quantum discord(GQD) between two qubits,each qubit interacting at the same time with K independent multiple bosonic reservoirs at zero temperature.In both weak and strong qubit-reservoirs coupling regimes,we find that the increase of the number K of reservoirs can induce the damped oscillation of GQD,and enhance the memory effects of the overall environment.And the Hilbert-Schmidt norm GQD(two-norm GQD) is always smaller than the trace norm geometric quantum discord(one-norm GQD).Therefore,the one-norm GQD is a better way to measure the quantum correlation.Finally,we propose an effective strategy to improve GQD by using partially collapsing measurements,and we find that the protection effect is better with the increase of the weak measurement strength.
基金supported by the National Natural Science Foundation of China (Grant No. 10974126)the National Basic Research Program of China (Grant No. 2010CB923102)
文摘In this paper, the frequency conversion of quantum states based on the intracavity nonlinear interaction is proposed. The fidelity of an input state after frequency conversion is calculated, and it is shown the noise-free frequency conversion of a quantum state can be achieved by injecting a strong signal field. The dependences of conversion efficiency on the pump parameter, extra losses and input state amplitude are also analysed.
基金Supported by the National Natural Science Foundation of China under Grant No 10974126the National Basic Research Program of China under Grant No 2010CB923102.
文摘The output amplitude noises of one squeezed probe light which is at resonance throughout different optical depths media in strong- and weak-coupling-field regimes are investigated theoretically.By comparing the output quantum noises for different Rabi frequencies of coupling field and also for different optical depths,it is found that the optimal squeezing preservation of the probe light occurs in an optically thin medium with strong-coupling-field,where we can obtain the output squeezing close to the input one at nonzero detection frequency.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61925503, 11874038, and 11654002)the Key Project of the National Key R&D Program of China (Grant Nos. 2016YFA0301402 and 2020YFA0309400)+2 种基金the Program for the Innovative Talents of Higher Education Institutions of Shanxithe Program for Sanjin Scholars of Shanxi Provincethe Fund for Shanxi “1331 Project” Key Subjects Construction
文摘Non-Hermitian systems have observed numerous novel phenomena and might lead to various applications.Unlike standard quantum physics,the conservation of energy guaranteed by the closed system is broken in the non-Hermitian system,and the energy can be exchanged between the system and the environment.Here we present a scheme for simulating the dissipative phase transition with an open quantum optical system.The competition between the coherent interaction and dissipation leads to the second-order phase transition.Furthermore,the quantum correlation in terms of squeezing is studied around the critical point.Our work may provide a new route to explore the non-Hermitian quantum physics with feasible techniques in experiments.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural National Science Foundation of China(Grant Nos.11604392 and 11674200)+1 种基金the Changjiang Scholars and Innovative Research Team in Universities of Ministry of Education of China(Grant No.IRT 17R70)the Fund for Shanxi“1331 Project”Key Subjects Construction,and the 111 Project,China(Grant No.D18001).
文摘We present a protocol to realize topological discrete-time quantum walks,which comprise a sequence of spindependent flipping displacement operations and quantum coin tossing operations,with a single trapped ion.It is demonstrated that the information of bulk topological invariants can be extracted by measuring the average projective phonon number when the walk takes place in coherent state space.Interestingly,the specific chiral symmetry owned by our discrete-time quantum walks simplifies the measuring process.Furthermore,we prove the robustness of such bulk topological invariants by introducing dynamical disorder and decoherence.Our work provides a simple method to measure bulk topological features in discrete-time quantum walks,which can be experimentally realized in the system of single trapped ions.
文摘This paper describes the generation and observation of sub-Poissonian light in an open-loop system with low quantum efficiency at room temperature.The experimental results show that the photocurrent Huctuation spectrum density can be reduced below the shot noise limit by 72%(-5.5 dB)in an open-loop light-emitting diode(LED)system at the frequency of 2MHz.The noise reduction is not limited by quantum efficiency of the LEDr or the current transfer efficiency.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60736040 and 10674089, the NSFC/RGC Joint Research Programme （No 60518001）, and National Basic Research Programme of China under Grant No 2006CB921101.
文摘We propose a scheme for the simultaneously preparation radiation-field modes of a single photon and a superposition of zero- and one-photon states, based on the coherent quantum state displacement and photon subtraction from two-mode squeezed state. It is shown that the single-photon and the superposition states can be obtained by only choosing the suitable parameter of displacements. The experimental feasibility to accomplish this scheme is also discussed.
基金supported by the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302003)the National Key Research and Development Program of China (Grant Nos. 2022YFA1404101, 2018YFA0307601,and 2021YFA1401700)+1 种基金the National Natural Science Foundation of China (Grant Nos. 12034011, 92065108, 11974224, 12022406, and 12004229)the Fund for Shanxi 1331 Project Key Subjects Construction。
文摘We report a compact experimental setup for producing a quantum degenerate mixture of Bose23Na and Fermi40K gases. The atoms are collected in dual dark magneto–optical traps(MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D2line for23Na and D1line for40K. The microwave evaporation cooling is used to cool23Na in |F = 2, mF= 2〉 in an optically plugged magnetic trap, meanwhile,40K in |F = 9/2, mF= 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where23Na atoms are immediately transferred to |1, 1〉 for further effective cooling to avoid the strong three-body loss between23Na atoms in |2, 2〉 and40K atoms in |9/2, 9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of40K with 1.9 × 10^(5) atoms at T/TF= 0.5 in the |9/2, 9/2〉 hyperfine state coexists with a Bose–Einstein condensate(BEC) of23Na with 8 × 10^(4) atoms in the |1, 1〉 hyperfine state at 300 n K. We also can produce the two species mixture with the tunable population imbalance by adjusting the 23Na magneto–optical trap loading time.
文摘We construct a one-dimensional quasiperiodic quantum walk to investigate the localization–delocalization transition.The inverse participation ratio and Lyapunov exponent are employed as two indexes to determine the mobility edge, a critical energy to distinguish the energy regions of extended and localized states. The analytical solution of mobility edge is obtained by the Lyapunov exponents in global theory, and the consistency of the two indexes is confirmed. We further study the dynamic characteristics of the quantum walk and show that the probabilities are localized to some specific lattice sites with time evolution. This phenomenon is explained by the effective potential of the Hamiltonian which corresponds to the phase in the coin operator of the quantum walk.
基金the National NaturalScience Foundation of China (Grant No. 62175135)theSpecial Foundation of Local Scientific and TechnologicalDevelopment Guided by Central Government (GrantNo. YDZJSX20231A006)the Fundamental ResearchProgram of Shanxi Province (Grant No. 202103021224025).
文摘An optical-tweezers-based dual-frequency-band particle tracking system was designed and fabricated for liquid viscositydetection. On the basis of the liquid viscosity dependent model of the particle’s restricted Brownian motion with theFax´en correction taken into account, the liquid viscosity and optical trap stiffness were determined by fitting the theoreticalprediction with the measured power spectral densities of the particle’s displacement and velocity that were derived from thedual-frequency-band particle tracking data. When the SiO2 beads were employed as probe particles in the measurements ofdifferent kinds of liquids, the measurement results exhibit a good agreement with the reported results, as well as a detectionuncertainty better than 4.6%. This kind of noninvasive economical technique can be applied in diverse environments forboth in situ and ex situ viscosity detection of liquids.
基金supported by the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302003)the National Natural Science Foundation of China (Grant Nos. 12034011, U23A6004, 12374245,12322409, 92065108, 11974224, and 12022406)+1 种基金the National Key Research and Development Program of China (Grant Nos. 2022YFA1404101 and 2021YFA1401700)the Fund for Shanxi 1331 Project Key Subjects Construction。
文摘We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the ODT.We observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical trap.By optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the ODT.We experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are obtained.The ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.
