摘要
In this paper we present a necessary and sufficient condition of separability for multipartite pure states and variants of it. These conditions are very simple and calculable, and they do not require Schmidt decomposition （for two subsystems） or tracing out operations. We also give a necessary condition for a local unitary equivalence class for a bipartite system in terms of the determinant of the matrix of amplitudes.
基金
The project supported by National Natural Science Foundation of China under Grant No.60433050
the Fundamental Research Fund of Tsinghua University under Grant No.JC2003043
partially by the State Key Lab.of Intelligence Technology and System
