The general case in which the electric field rotates in the x–y plane and has variable magnitude is called elliptical polarization. The state vector is given by | ψ ψ ⟩ ⟩ = d e f ( ψ ψ x ψ ψ y ) = ( cos ⁡ ⁡ θ θ exp ⁡ ⁡ ( i α α x ) sin ⁡ ⁡ θ θ exp ⁡ ⁡ ( i α α y ) ) .