Crossing w=−1w=-1 by a single scalar field coupling with matter and the observational constraints

Motivated by Yang-Mills dark energy model, we propose a new model by introducing a logarithmic correction. we find that this model can avoid the coincidence problem naturally and gives an equation of state $w$ smoothly crossing -1 if an interaction between dark energy and dark matter exists. It has a stable tracker solution as well. To confront with observations based on the combined data of SNIa, BAO, CMB and Hubble parameter, we obtain the best fit values of the parameters with $1\sigma, 2\sigma, 3\sigma$ errors for the noncoupled model: $\Omega_m=0.276\pm0.008^{+0.016+0.024}_{-0.015-0.022}$, $h=0.699\pm0.003\pm0.006\pm0.008$, and for the coupled model with a decaying rate $\gamma=0.2$: $\Omega_m=0.291\pm0.004^{+0.008+0.012}_{-0.007-0.011}$, $h=0.701\pm0.002\pm0.005\pm0.007$. In particular, it is found that the non-coupled model has a dynamic evolution almost undistinguishable to $\Lambda$CDM at the late-time Universe.Comment: 12 pages, 3 figures, the published versio

Generation of cluster states

We propose two schemes for the generation of the cluster states. One is based on cavity quantum electrodynamics (QED) techniques. The scheme only requires resonant interactions between two atoms and a single-mode cavity. The interaction time is very short, which is important in view of decoherence. Furthermore, we also discuss the cavity decay and atomic spontaneous emission case. The other is based on atomic ensembles. The scheme has inherent fault tolerance function and is robust to realistic noise and imperfections. All the facilities used in our schemes are well within the current technology.Comment: Complete rewite version, adding the main results of quant-ph/0511045. 7 pages and 3 figure