Direct generation of bright quadripartite continuous-variable entanglement use cascaded χ2 nonlinear interactions in a quasiperiodic optical superlattice

The production of quadripartite continuous-variable entanglement, with different frequency, is analyzed theoretically. This process is realized by parametric amplifier cascaded with a sum frequency generation in a quasiperiodically optical supperlattice, meanwhile, the nondegenerated optical parametric amplifier operated above threshold and the injection signal field with very small intensity is in coherent state. It shows that the four-partite of the pump, two subharmonic and the up-converted modes from the cavity is genuinely entangled according to the sufficient inseparability criterion proposed by Van Loock and Furusawa. Moreover, the entanglement characteristics versus different parameters are discussed as well in detail.