THE GEOMETRICAL PICTURE OF MIXED ENTANGLED STATES
混合纠缠态的几何描述

The vector representation of density matrix is given in this paper. Any density matrix can be expanded in a real linear Hilbert space. The criteria for insepara bility of mixed states can be expressed in the geometrical picture. Such express ion is concise and perceptible. The neighborhood of the maximal mixed state is analyzed and a stronger result about the volume measure of the neighborhood is obtained.