Generation of Quadripartite Entangled Light Field with Continuous Variable at Different Frequencies

The quantum entangled state is the key resource of quantum information. A feasible experimental scheme is proposed that a sum-frequency process is cascaded by a non-degenerate optical parametric oscillation with an injection signal in an optical superlattice, which can generate quadripartite continuous variable entangled light fields with different frequencies. First, the pump light and the injected signal light generate idle light through the difference frequency process. Then, the pump light and idle light generate sum-frequency light through a cascaded sum-frequency process in the same optical superlattice. According to the determination method of multi-component continuous variable entanglement, the characteristics of quantum entanglement among pump light, signal light, idle light, and sum-frequency light field are theoretically proved. The quadripartite entanglement characteristic decreases with the increase of pump power, and a better quadripartite entangled light field can be obtained by selecting larger injection signal power, coupling parameters of cascade nonlinear process and pump light attenuation constant. In this experimental scheme, a four-color continuous variable entangled light field can be generated by using only one optical superlattice, and the experimental device is simple.