The time evolution of the squeezing factors of a three-level atom. The atom is in a coherent superposition state with θ = π/3, φ = arcsin ( 6 / 3 ) , and the field is the coherent state with initial average photon number n ¯ = | α | 2 = 225 ; (a) entropy squeezing factor E ( S x ) ; (b) entropy squeezing factor E ( S y ) ; (c)variance squeezing factor V ( S x ) ; (d) variance squeezing factor V ( S y ) .