Ming Li, Shao-Ming Fei and Zhi-Xi Wang 1 Department of Mathematics, Capital Normal University, Beijing 100037 2 Institut für Angewandte Mathematik, Universität Bonn, D-53115 Abstract We study the concurrence of arbitrary multipartite mixed quantum states. An explicit lower bound of the concurrence is derived, which detects quantum entanglement of some states better than some separability criter...