title: Generation of four-photon polarization entangled decoherence-free states with cross-Kerr nonlinearity.
abstract: We propose a theoretical protocol for preparing four-photon polarization entangled decoherence-free states, which are immune to the collective noise. With the assistance of the cross-Kerr nonlinearities, a two-photon spatial entanglement gate, two controlled-NOT gates, a four-photon polarization entanglement gate are inserted into the circuit, where X homodyne measurements are aptly applied. Combined with some swap gates and simple linear optical elements, four-photon polarization entangled decoherence-free states which can be utilized to represent two logical qubits, |0〉Land |1〉Lare achieved at the output ports of the circuit. This generation scheme may be implemented with current experimental techniques.
authors.affiliation: College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Meiyu
authors.initials: M
authors.lastname: Wang
authors.affiliation: College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Fengli
authors.initials: F
authors.lastname: Yan
authors.affiliation: College of Mathematics and Information Science, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Gao