Algebraic approach in unifying quantum integrable models

A novel algebra underlying integrable systems is shown to generate and unify a large class of quantum integrable models with given $R$-matrix, through reductions of an ancestor Lax operator and its different realizations. Along with known discrete and field models a new class of inhomogeneous and impurity models are obtained.Comment: Revtex, 6 pages, no figure, revised version to be published in Phys. Rev. Lett., 199

Wigner functions, squeezing properties and slow decoherence of atomic Schrodinger cats

We consider a class of states in an ensemble of two-level atoms: a superposition of two distinct atomic coherent states, which can be regarded as atomic analogues of the states usually called Schrodinger cat states in quantum optics. According to the relation of the constituents we define polar and nonpolar cat states. The properties of these are investigated by the aid of the spherical Wigner function. We show that nonpolar cat states generally exhibit squeezing, the measure of which depends on the separation of the components of the cat, and also on the number of the constituent atoms. By solving the master equation for the polar cat state embedded in an external environment, we determine the characteristic times of decoherence, dissipation and also the characteristic time of a new parameter, the non-classicality of the state. This latter one is introduced by the help of the Wigner function, which is used also to visualize the process. The dependence of the characteristic times on the number of atoms of the cat and on the temperature of the environment shows that the decoherence of polar cat states is surprisingly slow.Comment: RevTeX, 14 pages including 8 PostScript figures. High quality versions of Figures 1, 3, 5, 7 and 8 are available at http://www.jate.u-szeged.hu/~benedict/asc_figures.html . (Submitted to Physical Review A: March 26, 1999.