The entanglement and squeezing properties of a two-mode field are investigated in the system of a double-ladder four-level atom embedded in a two-mode cavity. It is found that the system can reduce to the nondegenerate parametric oscillator which is responsible for the entanglement and squeezing of a cavity field under suitable conditions. Moreover, compared to the field from the three-level cascade atomic system, the degree of entanglement in...
