Thus, | ψ ψ c ( p ) ⟩ ⟩ and | ψ ψ e ( p ) ⟩ ⟩ undergo Sisyphus-like cooling, identifying the former as the bright state. | ψ ψ n c ( p ) ⟩ ⟩ is optically inaccessible and constitutes the dark state. However, | ψ ψ c ( p ) ⟩ ⟩ and | ψ ψ n c ( p ) ⟩ ⟩ are not eigenstates of the momentum operator, and thus motionally couple to one another via the kinetic energy term of the unperturbed Hamiltonian: