Quantifying decoherence in a many spin system

PABLO RENÉ ZANGARA; AXEL DAMIÁN DENTE; PATRICIA R. LEVSTEIN; HORACIO MIGUEL PASTAWSKI

Buenos Aires

Workshop; Autumn College on Non-Equilibrium Quantum Systems; 2011

Centro Internacional de Física Teórica (ICTP) Abdus Salam

The coherence in a quantum channel (spin 1/2 chain with XY interaction) is lost when the channel interacts with a non-controlled one (environment). The coherence loss can be evaluated by means of the recurrences attenuation (mesoscopic echoes) that arise from the finite size of the channel [1]. We compute equivalent coherence times evaluating the reversibility of the dynamics in the controlled channel, when it is coupled to the environment (not reversed). An initial local excitation evolves until the dynamics of the controlled channel is reversed. After the symmetric backward evolution, the reversibility is given by the Local Loschmidt Echo. This numerical analysis is complemented with an analytical calculation of decay rates, using a self consistent Fermi Golden Rule scheme. Fermionic modelization is also used in order to explain the dynamics of the polarization transfer. [1] E. P. Danieli, G. A Alvarez, P. R. Levstein, and H. M. Pastawski, Phys. Rev. A 82, 012310(2010).