2002/09/30 by Marco Frasca
Physics and Astronomy · Mathematics · #quant-ph #cond-mat.mes-hall #math-ph #math.MP #physics.atom-ph
paper · pdf · doi:10.1016/s0003-4916(03)00078-2
published as Annals of Physics 306, 193-208 (2003) · 20 pages, no figures. Revised version accepted for publication in Annals of Physics
arxiv created 2003/02/27 · arxiv updated 2009/11/30
The paradigm of the two-level atom is revisited and its perturbative analysis is discussed in view of the principle of duality in perturbation theory. The models we consider are a two-level atom and an ensemble of two-level atoms both interacting with a single radiation mode. The aim is to see how the latter can be actually used as an amplifier of quantum fluctuations to the classical level through the thermodynamic limit of a very large ensemble of two-level atoms [M. Frasca, Phys. Lett. A \bf 283, 271 (2001)] and how can remove Schrödinger cat states. The thermodynamic limit can be very effective for producing both classical states and decoherence on a quantum system that evolves without dissipation. Decoherence without dissipation is indeed an effect of a single two-level atom interacting with an ensemble of two-level atoms, a situation that proves to be useful to understand recent experiments on nanoscale devices showing unexpected disappearance of quantum coherence at very low temperatures.