We propose how to prepare four remote logical qubits, with each in a separate cavity and encoded in the decoherence-free subspace by two atoms, into various entangled states. By means of the cavity-assisted photon scattering, we can link the four remote logical qubits in different cavities to be, respectively,
W state, Greenberger-Horne-Zeilinger state, and cluster state, which are important in view of the distributed quantum information processing. The generation of the latter two entangled states can be theoretically generalized to many-qubit cases. Because our qubits are defined in dephasing-free subspace, our scheme is immune to dephasing during or even after the entanglement preparation.
Based on the interference effect of polarized photons leaking out of separate cavities, we propose schemes for the generation of the N -atom Greenberger–Horne–Zeilinger (GHZ) state, three-atom W state and a genuine four-atom entangled state |χ⟩. In these schemes, each of the atoms is trapped separately in a remote optical cavity, and the possible spontaneous channels induced by the excited atoms lead to the coherent superposition of the states of the atoms. The desired multipartite entangled states can be generated with a certain success probability by the subsequent detection of the polarized photons in different modes. The schemes would be useful steps towards long-distance quantum communication, distributed quantum computation and constructing remote quantum information processing networks.
We propose a scheme for generating a four-dimensional entanglement between two atoms trapped in two separate cavities connected by an optical fiber. Based on quantum Zeno dynamics, the entangled state is obtained only in one step. We also numerically investigate the influence of photon leakage and atomic spontaneous emission on the fidelity of the entangled state. The result shows that our scheme is robust against the cavity decay and very promising for realization with current experimental technology.