Nonadiabatic effects on population transfer of two Bose－Einstein condensates induced by atomic interaction

We investigate the stimulated Raman adiabatic passage for Bose－Einstein condensate (BEC) states which are trapped in different potential wells or two ground states of BEC in the same trap. We consider that lasers are nearly resonant with the atomic transitions. The difference of population transfer processes between BEC atoms and usual atoms is that the atomic interaction of the BEC atoms can cause some nonadiabatic effects, which may degrade the process. But with suitable detunings of laser pulses, the effects can be remedied to some extent according to different atomic interactions.     

Nonadiabatic effects on population transfer of two Bose-Einstein condensates induced by atomic interaction

We investigate the stimulated Raman adiabatic passage for Bose-Einstein condensate (BEG) states which are trapped in different potential wells or two ground states of BEG in the same trap. We consider that lasers are nearly resonant with the atomic transitions. The difference of population transfer processes between BEG atoms and usual atoms is that the atomic interaction of the BEG atoms can cause some nonadiabatic effects, which may degrade the process. But with suitable detunings of laser pulses, the effects can be remedied to some extent according to different atomic interactions.     

Evolution and Collision of Bose—Condensed Gas in One—Dimensional Optical Lattices and a Far—Off Resonant Laser Beam

Evolution of a Bose-condensed gas in one-dimensional optical lattices is investigated in the presence of a potentialbarrier created by a far-off resonant laser beam. After the magnetic trap and optical lattices are switched off,by using the propagator method, the analytical result of the evolution of the density distribution of the Bose-condensed gas is given. In particular, the collision between the condensate and the potential barrier is shown inthis paper.     

新世纪的第一只燕子--2001年度诺贝尔物理学奖述评

文章介绍了玻色－爱因斯坦凝聚的原理，着重讨论了2001年诺贝尔物理学奖得主：科耐尔（E.A.Cornell)、维曼（C.E.Wiemian)和凯特利（W.Ketterle)在世界上首次产生铷原子和钠原子的玻色－爱因斯坦凝聚的贡献，以及最近他们在玻色－爱因斯坦凝聚物理的研究和实现原子激射的诸多进展。并对玻色－爱因斯坦凝聚物理的发展与技术上的应用进行初步展望。     

The dispersive properties of an excited-doubletfour-level atomic system

We have investigated the dispersive properties of excited-doublet four-level atoms interacting with a weak probe field and an intense coupling laser field. We have derived an analytical expression of the dispersion relation for a general excited-doublet four-level atomic system subject to a one-photon detuning. The numerical results demonstrate that for a typical rubidium D1 line configuration, due to the unequal dipole moments for the transitions of each ground state to double excited states, generally there exists no exact dark state in the system. Close to the two-photon resonance, the probe light can be absorbed or gained and propagate in the so-called superluminal form. This system may be used as an optical switch.     

A remark on the condensation in the hard-core lattice Bose gas

We point out that Bose-Einstein condensation occurs at sufficiently low temperature in a hard-core ^d-lattice Bose gas for d3 and particle density 1/2, by exploiting its equivalence to a spin-1/2XY model.     

On the Bose gas with local mean-field interaction

A Bose gas model is considered where the interaction term is proportional to the integral over the square of the local particle density. This model exhibits a phase transition with the same critical behavior as the usual mean-field (imperfect) Bose gas, but only generalized condensation may occur, due to boundary conditions.     

Quantum corrections to the energy density of a homogeneous Bose gas

Quantum corrections to the properties of a homogeneous interacting Bose gas at zero temperature can be calculated as a low-density expansion in powers of , where is the number density and a is the S-wave scattering length. We calculate the ground state energy density to second order in . The coefficient of the correction has a logarithmic term that was calculated in 1959. We present the first calculation of the constant under the logarithm. The constant depends not only on a, but also on an extra parameter that describes the low energy scattering of the bosons. In the case of alkali atoms, we argue that the second order quantum correction is dominated by the logarithmic term, where the argument of the logarithm is ,and is the length scale set by the van der Waals potential. Received 2 February 1999     

Fully quantum mechanical moment of inertia of a mesoscopic ideal Bose gas

The superfluid fraction of an atomic cloud is defined using the cloud's response to a rotation of the external potential, i.e. the moment of inertia. A fully quantum mechanical calculation of this moment is based on the dispersion of L_z instead of quasi-classical averages. In this paper we derive analytical results for the moment of inertia of a small number of non-interacting Bosons using the canonical ensemble. The required symmetrized averages are obtained via a representation of the partition function by permutation cycles. Our results are useful to discriminate purely quantum statistical effects from interaction effects in studies of superfluidity and phase transitions in finite samples. Received 30 June 2000     

Kramers-Kronig type of dispersion relation in nonlinear optics

The applicability of Kramers-Kronig (K-K) relation under nearly sharp resonant transition regime in narrow-gap semiconductors has been established and consequently, a generalized dispersion relation for nonlinear optical susceptibility of a dielectric is derived. This relation can be employed in the study of nonlinear optical processes in solids as well as in plasmas over a wide frequency spectrum.     

Upper bound on the condensate in the hard-core Bose lattice gas

Using methods developed by G. Roepstorf, we prove an upper bound for the amount of condensate in ahard-core Bose lattice gas.On leave from the Mathematical Institute of the Hungarian Academy of Sciences, Budapest, H-1053, Hungary.     

Fluctuations in the population of the ground state of Bose Systems

Formulas are given which show how the fluctuations of the ground-state occupation number in a Bose System are strongly suppressed at low temperatures.