Chin. Phys., 2007, Vol. 16(12): 3595-3600    DOI: 10.1088/1009-1963/16/12/007
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# Entanglement in a generalized Jaynes--Cummings model

Zhang Guo-Feng, Liu Jia
Department of Physics, School of Sciences, Beijing University of Aeronauticsand Astronautics, Beijing 100083, China
Abstract  We investigate the pairwise entanglement and global entanglement in a generalized Jaynes--Cummings model, which can be used to realize Greenberger--Horne--Zeilinger (GHZ) entangled state (Zheng S B 2001 {\it Phys. Rev. Lett.} {\bf 87} 230404). Our results show that the W-type entangled states cannot be generated based on the model. The dependences of entanglement on Rabi frequency $\lambda$ and dipole--dipole coupling strength ${\it \Omega}$ are given. It is found that there exists the quantum phase transition when $\lambda={\it \Omega}$. For typical experimental data, the critical temperature for pairwise entanglement is on the order of $10^{-6}$\,K. Based on these results, two strategies that overcome decoherence are proposed.
Keywords:  dipole--dipole coupling strength      decoherence      thermal entanglement
Published:  20 December 2007
 PACS: 42.50.Dv (Quantum state engineering and measurements)
Fund: Project supported by the National Nature Science Foundation of China (Grant No 10604053).