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Decoherence and the Loschmidt echo

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 نشر من قبل Fernando M. Cucchietti
 تاريخ النشر 2003
  مجال البحث فيزياء
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Environment--induced decoherence causes entropy increase. It can be quantified using, e.g., the purity $varsigma={rm Tr}rho^2$. When the Hamiltonian of a quantum system is perturbed, its sensitivity to such perturbation can be measured by the Loschmidt echo $bar M(t)$. It is given by the average squared overlap between the perturbed and unperturbed state. We describe the relation between the temporal behavior of $varsigma(t)$ and $bar M(t)$. In this way we show that the decay of the Loschmidt echo can be analyzed using tools developed in the study of decoherence. In particular, for systems with a classically chaotic Hamiltonian the decay of $varsigma$ and $bar M$ has a regime where it is dominated by the classical Lyapunov exponents



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