Quantum dynamics under coherent and incoherent effects of a spin bath in the Keldysh formalism: application to a spin swapping operation

ERNESTO PABLO DANIELI; HORACIO MIGUEL PASTAWSKI; GONZALO AGUSTÍN ÁLVAREZ

CHEMICAL PHYSICS LETTERS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2005 vol. 402 p. 88 - 95

0009-2614

We develop the Keldysh formalism for the polarization dynamics of an open spin system. We apply it to the swapping between two qubit states in a model describing an NMR cross-polarization experiment. The environment is a set of interacting spins. For fast fluctuations in the environment, the analytical solution shows effects missed by the secular approximation of the quantum master equation for the density matrix: a frequency decrease depending on the system-environment escape rate and the quantum quadratic short time behavior. Considering full memory of the bath correlations yields a progressive change of the swapping frequency.