Quantum interference and quantum-Zeno effect in amplification without inversion

We analyze amplification without inversion (AWI) in different homogeneously broadened closed three-level systems in the framework of both density-matrix and quantum-jump formalisms. With the density-matrix formalism we study the nature of quantum interference in these systems; determine analytically the condition for AWI and locate the position of maxima and minima in the probe absorption spectrum. Within the quantum-jump formalism we calculate the relative probabilities of the various physical processes responsible for probe field amplification and absorption, and analyze the role of the quantum-Zeno effect in AWI. The result is that AWI in the h and p schemes is due to one-photon processes while for V and Λ schemes are due to two-photon processes. We also show that AWI in V and h schemes always occurs in the quantum-Zeno regime, while this regime is not necessary for AWI in the Λ and p schemes. Copyright © 1999 by MANK "Hayκa/Interperiodica".