Negative quantum conditional entropy and the entanglement measure of a kind of mixed state of bipartite quantum system
Zhou Bing-Ju, Xiaojuan Liu, Mao-Fa Fang, Zhou Qing-Ping, Mingwei Liu, (1)湖南科技大学物理学院，湘潭 411201; (2)湖南科技大学物理学院，湘潭 411201;湖南师范大学物理与信息学院，长沙 410081;中国科学院安徽光学精密机械研究所，合肥 230031; (3)湖南师范大学物理与信息学院，长沙 410081;中国科学院安徽光学精密机械研究所，合肥 230031 · Acta Physica Sinica · 2007
From negative quantum conditional entropy point of view this paper intestigates the entanglement measure of the prue state and a kind of mixed state of bipartite quantum system. Also this paper gives a definition of quantum conditional entropy of entanglement EA｜B(ρAB) and proves that it satisfies the four fundamental conditions of a entanglement measure for a kind of mixed state of 2×2 quantum system by this negative quantum conditional entropy Using conditional entropy of entanglement, this paper investigates the quantum entanglement between the two identical two-level atoms simultaneously interacting with vacuum cavity field as an application. This paper compares conditional entropy of entanglement and concurrence at the same condition, and the result shows that the curves of their evolvements are identical. These obtained results test and verifys that conditions of an entanglement measure may be taken as the entanglement measure of the prue state and a kind of mixed state of bipartite quantum system.