This paper studies the average fidelity of teleportation and thermal entanglement for a two-qubit Heisenberg XYZ chain in the presence of both an inhomogeneous magnetic field and a Dzyaloshinski-Moriya interaction. It shows that for a fixed Dz, the increase of bz will broaden the critical temperature at the cost of decreasing the thermal entanglement. And it can modulate the inhomogeneous magnetic field and the Dzyaloshinski-Moriya interaction for the average fidelity of teleportation to be optimal.
This paper presents a modified secure direct communication protocol by using the blind polarization bases and particles＇ random transmitting order. In our protocol, a sender （Alice） encodes secret messages by rotating a random polarization angle of particle and then the receiver （Bob） sends back these particles as a random sequence. This ensures the security of communication.
This paper proposes a scheme to generate a new x-type four-atom entangled state for the first time by using linear optics elements, four one-sided cavities （one three-level atom） and a conventional photon detector. The linear optical elements and conventional photon detector are simple and accessible in experiments, which makes the scheme more feasible with current technology. In addition, the state ｜X^00）3214 with probability 1 can be generated as long as there is no photon loss.
This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom （as target qubit） sent through a two-mode cavity （as control qubits）. The first scheme is based on the large-detuning atom cavity field interaction and the second scheme is based on the resonant atom-field interaction. Both the situations with and without cavity decay and atomic spontaneous emission are considered. The advantages and the experimental feasibility of these two schemes are discussed.
