Quantum Dynamics of Bound Entangled States

By using the partial transpose and realignment method,we study the time evolution of the bound entan-glement under the bilinear-biquadratic Hamiltonian.For the initial Horodeeki’s bound entangled state,it keeps boundentangled for some time,while for the initial bound entangled states constructed from the unextendable product basis,they become free once the time evolution begins.The time evolution provides a new way to construct bound entangledstates,and also gives a method to free bound entanglement.