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The thermal entanglement of a three-qubit Heisenberg chain under a nonuniform magnetic field is studied. It is very interesting to note that the next nearest neighbor entanglement (NNNE) could be larger than the nearest neighbor entanglement (NNE). We analyze the ground state entanglement, and give the conditions that NNNE is larger than NNE near zero temperature. Our results also show that the nonuniform field could induce the entanglement and improve the threshold temperature at certain parameter region.

Transmitting quantum states by channels of analogous Bell states is studied in this paper. We analyse the transmitting process, constructed the probabilitic unitary operator, and gain the largest successful transfer quantum state probability., 4 pages

The effects of different time-independent and time-dependent couplings on two-atom entanglement are studied. The results show that the effects depend on the initial state. For the initial state |ee0, it is found that different time-independent couplings make the case without entanglement exhibit entanglement, and time-dependent couplings turn the irregular entanglement regions into regular one. Under the case of decay, for the initial state |eg0, the different time-dependent couplings have disbenefit.