Entanglement purification without controlled-NOT gates by using the natural dynamics of spin chains

We present a simple protocol to purify bipartite entanglement in spin-1/2 particles by utilizing only natural spin-spin interactions, i.e., those that can commonly be realized in. realistic physical systems and S, measurements on single spins. Even the standard isotropic Heisenberg interaction is shown to be sufficient to purify mixed state entanglement. Our protocol does not need controlled-NOT (CNOT) gates that are very hard to implement experimentally. This approach could be useful for quantum-information processing in solid-statebased systems.