Groundstates of SU(2)-Symmetric Confined Bose Gas: Trap for a Schr\"odinger Cat

Conservation of the total isotopic spin S of a two-component Bose gas-like $^{87}$Rb-has a dramatic impact on the structure of the ground state. In the case when S is much smaller than the total number of particles N, the condensation of each of the two components occurs into two single-particle modes. The quantum wavefunction of such a groundstate is a Schr\"odinger Cat-a superposition of the phase separated classical condensates, the most "probable" state in the superposition corresponding to the classical groundstate in the sector of given N and S. After measurement of the spatial distribution of the densities of the two components, the Cat collapses into one of the classical condensate states.Comment: 5 RevTex pages, no figures; replaced with revised version, where the discussion on stability against temporal white noise and losses is adde

Detecting Super-Counter-Fluidity by Ramsey Spectroscopy

Spatially selective Ramsey spectroscopy is suggested as a method for detecting the super-counter-fluidity of two-component atomic mixture in optical lattice.Comment: 3pages, no figures, replaced with revised version accepted by PRA. Discussion of the Ramsey pattern specific for topological excitations is adde

Atomic Josephson vortex

We show that Josephson vortices in a quasi-1D atomic Bose Josephson junction can be controllably manipulated by imposing a difference of chemical potentials on the atomic BEC waveguides forming the junction. This effect, which has its origin in the Berry phase structure of a vortex, turns out to be very robust in the whole range of the parameters where such vortices can exist. We also propose that a Josephson vortex can be created by the phase imprinting technique and can be identified by a specific tangential feature in the interference picture produced by expanding clouds released from the waveguides.Comment: 7 pages, 3 figures, revtex4, submitted to Phys. Rev. A, title and abstract changed, old sections revised, new sections added, references adde