Fragility of superposition states evaluated by the Loschmidt echo

DENISE BENDERSKY; PABLO RENÉ ZANGARA; HORACIO MIGUEL PASTAWSKI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Lugar: New York; Año: 2013 vol. 88 p. 321021 - 3210210

1050-2947

We consider the degradation of the dynamics of a Gaussian wave packet in a harmonic oscillator under the presence of an environment. This last is given by a single nondegenerate two-level system. We analyze how the binary degree of freedom perturbs the free evolution of the wave packet producing decoherence, which is quantified by the Loschmidt echo. This magnitude measures the reversibility of a perturbed quantum evolution. In particular, we use it here to study the relative ?fragility? of coherent superpositions (cat states) with respect to incoherent ones. This fragility or sensitivity turns out to increase exponentially with the energy separation of the two components of the superposition.