The Lower Bounds Of Concurrence Of Some Quantum States

Quantum entanglement is a key resource in quantum information and quantum com-putation, and the research on entanglement measures is a hot spot. Concurrence is a goodentanglement measure. In this paper, some states’ lower bounds of concurrence whichare got by using the generalization of Wootters formula are studied.First, we introduce some useful background knowledge. For example, the definitionof quantum state, quantum entanglement state, density operator, concurrence, and soon.In second chapter, we introduce the results of concurrence’s lower bound of two-body system by using the generalization of Wootters formula, and use this method tocalculate the concurrence’s lower bounds of the Isotropic states, Werner states, Horodeck-i states, and so on, and for some states we even get the analytic expression of concurrence.