Five-partite entanglement generation between two optical frequency combs in a quasi-periodic χ((2)) nonlinear optical crystal

We theoretically prove five-partite entanglement can be produced among modes of two simultaneously generated optical frequency combs via second-order nonlinear interaction in a designed periodically poled lithium niobat (PPLN) crystal. An extendible model is proposed to analyze the entanglement characteristics of generated comb modes by applying van Loock and Furusawa criteria. Our proposal provides a potential approach for generating multipartite entangled states, the so-called cluster states, which are the key resources for quantum computation. Moreover, simultaneously generation of two entangled combs can provide much higher efficiency to generate cluster states.