Quantum Engineering of Superdark Excited States in Arrays of Atoms

Abstract

We suggest a regular method of achieving an extremely long lifetime of a collective singly excited state in a generic small-size ensemble of N identical atoms. The decay rate \Gamma_N of such a `superdark' state can be as small as \Gamma_N \propto \Gamma(r/\lambda)^{2(N-1)} (\Gamma is the radiative decay rate of an individual atom, r and \lambda are the system size and the wavelength of the radiation, respectively), i.e., considerably smaller than in any of the systems suggested up to now. The method is based on a special fine tuning of the atomic Hamiltonian: namely, on a proper position-dependent adjustment of atomic transition frequencies. So chosen set of the control parameters is sufficient to ensure the minimum of the spontaneous decay rate of the engineered state in a generic ensemble of atoms (`qubits').