The representation is always unique, because, even though the value of ϕ ϕ is not unique when | ψ ψ ⟩ ⟩ is one of the states (see Bra-ket notation) | 0 ⟩ ⟩ or | 1 ⟩ ⟩ , the point represented by θ θ and ϕ ϕ is unique.