Quantum Statistical Properties in Two—Species Bose—Einstein Condensates

We have studied quantum statistical properties in a zero-temperature two-species Bose-Einstein condensate system in the presence of the nonlinear self-interaction of each species,the interspecies nonlinear interaction,and the Jisephson-like tunneling interaction.It is found that the two condensates may periodically exhibit sub-Poissonian distribution.It is revealed that the correlation between the two condensates can be nonclassical,which means that there exists a violation of Cauchy-Schwartz inequality.The nonclassical effect about the correlation between the two condensates can be realized experimentally by properly preparing the total number of atoms in the two condensates.     

Dark Lump Excitations in Bose—Einstein Condensates

We investigate the dynamics of two-dimensional matter-wave pulses in a Bose-Einstein condensate with diskshaped traps.For the case of repulsive atom-atom interactions,a Kadomtsev-Petviashvili equation with positive dipersion is derived using the method of multiple scales.The results show that it is possible to excite dark lump-like two-dimensional nonlinear excitations in the Bose-Einstein condensate.     

Quantum Dynamics of Cooled Atoms in the Presence of Bose—Einstein Condensates

Under the Markov approximation,the quantum dynamics of cooled atoms in the presence of Bose-Einstein condensates is studied.A master equation governing the evolution of such a system is derved.Using this master equation,the distribution of the atoms in the excited states at finite temperature and the dynamics of the excited atom at zero temperature are given and discussed.     

Stimulated Raman Adiabatic Population Transfer of Two Bose—Einstein Condensates

Considering all the ground-state atom interactions,we investigate the population transfer of two Bose-Einstein condensate (BEC) states,which are trapped in diffecent potential wells,or two ground states of the BEC in the same trap using the stimulated Raman adiabatic process.With a proper choice of pulsed geometric parameters,the dark state exists.By simply choosing ground-state detunings,the effects of the interatomic interaction can be suppressed and a high population transfer rate can be obtained.     

Self—Trapping State and Atomic Tunnelling Current of an Atomic Bose—Einstein Condensate Interacting with a Laser Field in a Double—Well Potential

We present a theoretical treatment of dynamics of an atomic Bose-Einstein condensation interacting with a single-mode quantized travelling-wave laser field in a double-well potential.When the atom-field system is initially in a coherent state,expressions for the energy exchange between atoms and photons are derived.It is revealed that atoms in the two wells can be in a self-trapping state when the tunnelling frequency satisfies two specific conditions,in which the resonant and far off-resonant cases are included.It is found that there is an alternating current with two different sinusoidal oscillations between the two wells,but no dc characteristic of the atomic tunnelling current occurs.It should be emphasized that when without the laser field,both the population difference and the atomic tunnelling current are only a single oscillation.But they will respectively become a superposition of two oscillations with different oscillatory frequencies in the presence of the laser field.For the two oscillations of the population difference,one always has an increment in the oscillatory frequency,the other can have an increment or a decrease under different cases.These conclusions are also suitable to those of the atomic tunnelling current.As a possible application,by measurement of the atomic tunnelling current between the two wells,the number of Bose-condensed atoms can be evaluated.By poperly selecting the laser field,the expected atomic tunnelling current can be obtained too.     

Rabi Oscillations in Two－Component Bose－Einstein COndensates with a Coupling Drive

The Rabi oscillations in two-component Bose-Einstein condensates with a coupling drive are studied by means of a pair of bosonic operators.The coupling drive and initial phase difference will affect the amplitude and the period of the Rabi oscillations.The Rabi oscillations will vanish in the evolution of the condensate density for some special initial phase differences(φ=0 or π).Our theory provides not only an analytical framework for quantitiative predictions for two-component condensates,but also gives an intuitive understanding of some mysterious features observed in experiments and numerical simulations.     

Tunneling Dynamics of Two-Species Bose-Einstein Condensates

We have studied the tunneling dynamics of two-species Bose-Einstein condensates. It is shown that the population difference and the Josephson-like tunneling current between the two condensates exhibit oscillation behaviors and there exists macroscopic quantum self-trapping, which strongly depends on the initial state, interatomic nonlinear self-interaction, interspecies nonlinear interaction, and the total number of atoms in the two condensates.     

Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive

In this paper, we have studied the atomic population difference and the atomic tunneling current of twocomponent Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose-Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of 10-10 ～ 10-9 second.     

Tunneling Dynamics of Two-Species Molecular Bose-Einstein Condensates

We study tunneling dynamics of atomic group in two-species molecular Bose-Einstein condensates. It is shown that the tunneling of the atom group depends on not only the tunneling coupling constant between the atomic pair molecular condensate and the three-atomic group molecular condensate, but also the inter-molecular nonlinear interactions and the initial number of atoms in these condensates. It is discovered that besides oscillating tunneling current between the atomic pair molecular condensate and the three-atomic group molecular condensate, the nonlinear atomic group tunneling dynamics sustains a self-maintained population imbalance: a macroscopic quantum self-trapping effect.     

Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive

In this paper, we have studied the atomic population difference and the atomic tunneling current of two-component Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of 10^-10 ～ 10^-9 second.     

Tunneling Dynamics of Two-Species Bose-Einstein Condensates with Feshbach Resonances

We investigate tunneling dynamics of atomic group consisting of three atoms in Bose-Einstein condensateswith Feshbach resonance. It is shown that the tunneling of the atom group depends not only on the inter-atomicnonlinear interactions and the initial number of atoms in these condensates, but also on the tunneling coupling betweenthe atomic condensate and the three-atomic molecular condensate. It is found that besides oscillating tunneling currentbetween the atomic condensate and the molecular condensate, the nonlinear atomic group tunneling dynamics sustains aself-maintained population imbalance: a macroscopic quantum self-trapping effect. The influence of de-coherence causedby non-condensate atoms on the tunneling dynamics is studied. It is indicated that de-coherence suppresses the atomicgroup tunneling.     

Tunneling Dynamics of Two-Species Bose-Einstein Condensates with Feshbach Resonances

We investigate tunneling dynamics of atomic group consisting of three atoms in Bose-Einstein condensates with Feshbach resonance. It is shown that the tunneling of the atom group depends not only on the inter-atomic nonlinear interactions and the initial number of atoms in these condensates, but also on the tunneling coupling between the atomic condensate and the three-atomic molecular condensate. It is found that besides oscillating tunneling current between the atomic condensate and the molecular condensate, the nonlinear atomic group tunneling dynamics sustains a self-maintained population imbalance: a macroscopic quantum self-trapping effect. The influence of de-coherence caused by non-condensate atoms on the tunneling dynamics is studied. It is indicated that de-coherence suppresses the atomic group tunneling.     

Tunneling Dynamics Between Atomic and Molecular Bose-Einstein Condensates

Tunneling dynamics of multi-atomic molecules between atomic and multi-atomic molecular Bose-Einstein condensates with Feshbach resonance is investigated.It is indicated that the tunneling in the two Bose-Einstein condensates depends on not only the inter-atomic-molecular nonlinear interactions and the initial number of atoms in these condensates,but also the tunneling coupling between the atomic condensate and the multi-atomic molecular condensate.It is discovered that besides oscillating tunneling current between the atomic condensate and the multi-atomic molecular condensate,the nonlinear multi-atomic molecular tunneling dynamics sustains a self-locked population imbalance:a macroscopic quantum self-trapping effect.The influence of de-coherence caused by non-condensate atoms on the tunneling dynamics is studied.It is shown that de-coherence suppresses the multi-atomic molecular tunneling.Moreover,the conception of the molecular Bose-Einstein condensate,which is different from the conventional single-atomic Bose-Einstein condensate,is specially emphasized in this paper.     

Tunneling of Spinor Bose-Einstein Condensates in Optical Lattice

In this letter, we have studied the tunneling effects and fluctuations of spinor Bose-Einstein condensates in optical lattice. It is found that there exist tunneling effects and fluctuations between lattices l and l ＋ 1, l and l - 1, respectively. In particular, when the optical lattice is infinitely long and the spin excitations are in the long-wavelength limit, tunneling effects disappear between lattices I and l＋ 1, and I and l - 1. In this case the fluctuations are a constant, and the magnetic soliton appears.     

Tunneling of Spinor Bose-Einstein Condensates in Optical Lattice

In this letter, we have studied the tunneling effects and fluctuations of spinor Bose-Einstein condensates in optical lattice. It is found that there exist tunneling effects and fluctuations between lattices l and l 1, l and l - 1,respectively. In particular, when the optical lattice is infinitely long and the spin excitations are in the long-wavelength limit, tunneling effects disappear between lattices l and l 1, and l and l - 1. In this case the fluctuations are a constant,and the magnetic soliton appears.     

Atomic Tunnelling Dynamics of Two Squeezed Bose-Einstein Condensates

In this paper, tunnelling dynamics of squeezed Bose-Einstein condensates (BEC's) in the presence of the nonlinear self-interaction of each species, the interspecies nonlinear interaction, and the Josephson-like tunnelling interaction is investigated by using the second quantization approach. The influence of BEC squeezing on macroscopic quantum self-trapping (MQST) and quantum coherent atomic tunnelling is analyzed in detail. It is shown that the MQST and coherent atomic tunnelling between two squeezed BEC's can be manipulated through changing squeezing amplitude and squeezing phase of BEC squeezed states.