Proposal to produce long-lived mesoscopic superpositions through an atom-driven field interaction

The mastery of techniques for preparing cavity-field states through atom-field interaction in cavity quantum electrodynamics (QED) is crucial to many useful applications in quantum optics. As high-Q cavities have permitted the preparation of cavity-field superpositions of the form |Ψ〉 = ∣α eiφ 〉 + ∣α e−iφ 〉) / √ 2, with mean number of oscillator quanta |α| ≈ 10, mesoscopic quantum coherence in cavity QED has been investigated: the progressive decoherence of the superposition |Ψ〉, involving radiation fields with classically distinct phases, was observed through atom-field interaction [1] and the reversible decoherence of such a cavity-field state has been conjectured [2]. In this letter we present a proposal for the achievement of long-lived mesoscopic superposition states in cavity QED which relies on two basic requirements: parametric amplification and an engineered squeezed-vacuum reservoir for cavity-field states. Our proposal considers the dispersive interaction of a two-level atom with a cavity field which is simultaneously under amplification processes. The parametric amplification is employed to achieve the required high degrees of squeezing and excitation