Decoherence and the Loschmidt echo

F. M. Cucchietti, D. A. R. Dalvit, J. P. Paz +1

Environment--induced decoherence causes entropy increase. It can be quantified using, e.g., the purity $\varsigma =\mathrm{Tr}{\rho }^2$. When the Hamiltonian of a quantum system is perturbed, its s…