Decoherence as attenuation of mesoscopic echoes in a spin-chain channel

An initial local excitation in a confined quantum system evolves, exploring the whole system and returning to the initial position as a mesoscopic echo at the Heisenberg time. We consider two weakly coupled spin chains, a spin ladder, where one is a quantum channel while the other represents an environment. We quantify decoherence in the quantum channel through the attenuation of the mesoscopic echoes. We evaluate decoherence rates for different ratios between sources of amplitude fluctuation and dephasing in the interchain interaction Hamiltonian. The many-body dynamics is seen as a one-body evolution with a decoherence rate given by the Fermi golden rule.