We study the nonequilibrium dynamics of the Quantum Ising Model following an
abrupt quench of the transverse field. We focus on the on-site autocorrelation
function of the order parameter, and extract the phase coherence time
τQϕ​ from its asymptotic behavior. We show that the initial state
determines τQϕ​ only through an effective temperature set by its
energy and the final Hamiltonian. Moreover, we observe that the dependence of
τQϕ​ on the effective temperature fairly agrees with that obtained
in thermal equilibrium as a function of the equilibrium temperature.Comment: 4 pages, 4 figures. Published versio