We study the phase coherence property of Bose-Einstein condensates confined in a one-dimensional optical lattice formed by a standing-wave laser field. The lattice depth is determined using a method of Kapitza-Dirac s...We study the phase coherence property of Bose-Einstein condensates confined in a one-dimensional optical lattice formed by a standing-wave laser field. The lattice depth is determined using a method of Kapitza-Dirac scattering between a condensate and a short pulse lattice potential. Condensates are then adiabatically loaded into the optical lattice. The phase coherence property of the confined condensates is reflected by the interference patterns of the expanded atomic cloud released from the optical lattice. For weak lattice, nearly all of the atoms stay in a superfluid state. However, as the lattice depth is increased, the phase coherence of the whole condensate sample is gradually lost, which confirms that the sub-condensates in each lattice well have evolved into number-squeezed states.展开更多
The interference pattern of two Bose–Einstein condensates released from a double-well potential for different holding times is theoretically investigated using a decoupled two-mode Bose–Hubbard model.For two coheren...The interference pattern of two Bose–Einstein condensates released from a double-well potential for different holding times is theoretically investigated using a decoupled two-mode Bose–Hubbard model.For two coherently separated condensates,the interference displays a periodic behavior,which is closely related to the atomic interaction.A remarkable parity effect is found in the interference patterns.For certain holding times,the even/odd total number of atoms would result in different interference fringes.The influences of different initial conditions on the evolution of interference and the observation of parity effects are discussed.展开更多
Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demon...Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demonstrate that the interference in the momentum distribution can be used to extract the correlation in the Bose gas. A simple relation between the interference visibility and the correlation length is found and used to interpret the pioneering experiment about the critical behavior of dilute Bose gases [Science 315 1556（2007）]. Our theory paves the way to experimentally study various types of ultra-cold atomic gases with the means of matter wave interference.展开更多
We experimentally investigate the collective excitation of 87Rb Bose-Einstein condensates confined in a cigarshaped magnetic trap （QUIC trap）. Using a method of magnetic perturbation, the center-of-mass oscillation ...We experimentally investigate the collective excitation of 87Rb Bose-Einstein condensates confined in a cigarshaped magnetic trap （QUIC trap）. Using a method of magnetic perturbation, the center-of-mass oscillation of the condensate is excited, so that the radial trapping frequency of the QUIC trap can be precisely determined. A high-order excitation, characterized by a fast shape oscillation, also occurs simultaneously, with a noticeable damping in the oscillation amplitude compared with the oscillation of the center of mass. The measured oscillation frequencies, associated with these two low-energy excitation modes, agree well with theoretical predictions based on the Gross-Pitaevskii equation.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10634060 and 10574142, and the National Basic Research Program of China under Grant Nos 2005CB724501 and 2006CB921406.
文摘We study the phase coherence property of Bose-Einstein condensates confined in a one-dimensional optical lattice formed by a standing-wave laser field. The lattice depth is determined using a method of Kapitza-Dirac scattering between a condensate and a short pulse lattice potential. Condensates are then adiabatically loaded into the optical lattice. The phase coherence property of the confined condensates is reflected by the interference patterns of the expanded atomic cloud released from the optical lattice. For weak lattice, nearly all of the atoms stay in a superfluid state. However, as the lattice depth is increased, the phase coherence of the whole condensate sample is gradually lost, which confirms that the sub-condensates in each lattice well have evolved into number-squeezed states.
基金by NSFC under Grant Nos 10804123 and 10875165NKBRSF of China under Grant No 2011CB921503.
文摘The interference pattern of two Bose–Einstein condensates released from a double-well potential for different holding times is theoretically investigated using a decoupled two-mode Bose–Hubbard model.For two coherently separated condensates,the interference displays a periodic behavior,which is closely related to the atomic interaction.A remarkable parity effect is found in the interference patterns.For certain holding times,the even/odd total number of atoms would result in different interference fringes.The influences of different initial conditions on the evolution of interference and the observation of parity effects are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504328,11274024,and 11334001)the National Basic Research Program of China(Grants Nos.2013CB921903 and 2012CB921300)
文摘Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demonstrate that the interference in the momentum distribution can be used to extract the correlation in the Bose gas. A simple relation between the interference visibility and the correlation length is found and used to interpret the pioneering experiment about the critical behavior of dilute Bose gases [Science 315 1556（2007）]. Our theory paves the way to experimentally study various types of ultra-cold atomic gases with the means of matter wave interference.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10634060 and 10574142, and the National Key Basic Research Program of China under Grant Nos 2005CB724501 and 2006CB921406.
文摘We experimentally investigate the collective excitation of 87Rb Bose-Einstein condensates confined in a cigarshaped magnetic trap （QUIC trap）. Using a method of magnetic perturbation, the center-of-mass oscillation of the condensate is excited, so that the radial trapping frequency of the QUIC trap can be precisely determined. A high-order excitation, characterized by a fast shape oscillation, also occurs simultaneously, with a noticeable damping in the oscillation amplitude compared with the oscillation of the center of mass. The measured oscillation frequencies, associated with these two low-energy excitation modes, agree well with theoretical predictions based on the Gross-Pitaevskii equation.
