We demonstrate a method for further reducing the cavity linewidth by the application of a small longitudinal magnetic field on the Rb cell. Because of the magnetic field multiple electromagnetically induced transparen...We demonstrate a method for further reducing the cavity linewidth by the application of a small longitudinal magnetic field on the Rb cell. Because of the magnetic field multiple electromagnetically induced transparen- cies （EITs） are observed. The center EIT linewidth is measured as a function of the magnetic field. By utilizing the center EIT we narrow the cavity linewidth to 2 MHz which is half of the cavity linewidth without magnetic field.展开更多
We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum d...We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum degeneracy： initial radio-frequency （RF） enforced evaporative cooling in the quadrupole magnetic trap and further runaway evaporative cooling in the optical dipole trap. The hybrid trap does not require a very high power laser such as that in the traditional pure optical trap, but still has a deep trap depth and a large trap volume, and has better optical access than the normal magnetic trap like the quadrupole-Ioffe-configuration （QUIC） cloverleaf trap. A high trap frequency can be easily realized in the hybrid trap to enhance the elastic collision rate and shorten the evaporative cooling time. In our experiment, pure Bose-Einstein condensates （BECs） with about 1 x 105 atoms can be realized in 6 s evaporative cooling in the optical dipole trap.展开更多
We numerically analyze the dynamic behavior of Bose–Einstein condensate(BEC)in a one-dimensional disordered potential before it completely loses spatial quantum coherence.We find that both the disorder statistics and...We numerically analyze the dynamic behavior of Bose–Einstein condensate(BEC)in a one-dimensional disordered potential before it completely loses spatial quantum coherence.We find that both the disorder statistics and the atom interactions produce remarkable effects on localization.We also find that the single phase of the initial condensate is broken into many small pieces while the system approaches localization,showing a counter-intuitive step-wise phase but not a thoroughly randomized phase.Although the condensates as a whole show less flow and expansion,the currents between adjacent phase steps retain strong time dependence.Thus we show explicitly that the localization of a finite size Bose–Einstein condensate is a dynamic equilibrium state.展开更多
We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross Pitaevskii equation. It is indicated that...We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.展开更多
Non-classical paired photons are generated by a four-wave mixing process in a far-detuning three-level system with cold atoms.A violation of the Cauchy–Schwartz inequality of a factor of 310 is observed.This phenomen...Non-classical paired photons are generated by a four-wave mixing process in a far-detuning three-level system with cold atoms.A violation of the Cauchy–Schwartz inequality of a factor of 310 is observed.This phenomenon shows that paired photons have a non-classical correlation.The experimental results are compared with theoretical results obtained using perturbation theory.The oscillation frequencies of the two-photon intensity correlation functions are in reasonable agreement with the effective Rabi frequencies of the coupling laser.However,we find that the dephasing rates(or decay rates)observed are far larger than the theoretical values.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91321101,11274112,61108028,and 61178031)the Fundamental Research Funds for the Central Universities(No.WM1313003)
文摘We demonstrate a method for further reducing the cavity linewidth by the application of a small longitudinal magnetic field on the Rb cell. Because of the magnetic field multiple electromagnetically induced transparen- cies （EITs） are observed. The center EIT linewidth is measured as a function of the magnetic field. By utilizing the center EIT we narrow the cavity linewidth to 2 MHz which is half of the cavity linewidth without magnetic field.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10974211)the National Basic Research Program of China (Grant No. 2011CB921504)the Research Project of Shanghai Science and Technology Commission, China (Grant No. 09DJ1400700)
文摘We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum degeneracy： initial radio-frequency （RF） enforced evaporative cooling in the quadrupole magnetic trap and further runaway evaporative cooling in the optical dipole trap. The hybrid trap does not require a very high power laser such as that in the traditional pure optical trap, but still has a deep trap depth and a large trap volume, and has better optical access than the normal magnetic trap like the quadrupole-Ioffe-configuration （QUIC） cloverleaf trap. A high trap frequency can be easily realized in the hybrid trap to enhance the elastic collision rate and shorten the evaporative cooling time. In our experiment, pure Bose-Einstein condensates （BECs） with about 1 x 105 atoms can be realized in 6 s evaporative cooling in the optical dipole trap.
基金Supported by the National Natural Science Foundation of China under Grant No.10974211the National Basic Research Program of China under Grant No.2011CB921504the Research Project of Shanghai Science and Technology Commission under Grant Nos.09DJ1400700 and 10DJ1400600.
文摘We numerically analyze the dynamic behavior of Bose–Einstein condensate(BEC)in a one-dimensional disordered potential before it completely loses spatial quantum coherence.We find that both the disorder statistics and the atom interactions produce remarkable effects on localization.We also find that the single phase of the initial condensate is broken into many small pieces while the system approaches localization,showing a counter-intuitive step-wise phase but not a thoroughly randomized phase.Although the condensates as a whole show less flow and expansion,the currents between adjacent phase steps retain strong time dependence.Thus we show explicitly that the localization of a finite size Bose–Einstein condensate is a dynamic equilibrium state.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10334050 and 10804115, the National Basic Research Program of China under Grant No 2006CB921202, and the Knowledge Innovation Project of Chinese Academy of Sciences.
文摘We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.
基金by the National Natural Science Foundation of China under Grant No 10804115the National Basic Research Program of China under Grant Nos 2006CB921202 and 2011CB921504+1 种基金the Knowledge Innovation Project of Chinese Academy of Sciencesthe Shanghai Committee of Science and Technology under Grant No 09DJ1400700.
文摘Non-classical paired photons are generated by a four-wave mixing process in a far-detuning three-level system with cold atoms.A violation of the Cauchy–Schwartz inequality of a factor of 310 is observed.This phenomenon shows that paired photons have a non-classical correlation.The experimental results are compared with theoretical results obtained using perturbation theory.The oscillation frequencies of the two-photon intensity correlation functions are in reasonable agreement with the effective Rabi frequencies of the coupling laser.However,we find that the dephasing rates(or decay rates)observed are far larger than the theoretical values.
