Qubit decoherence with an initial correlation

Decoherence of a qubit system interacting with a bosonic reservoir is considered when there is at most one excitation in the whole system and there is an initial correlation with the reservoir. An exact time-evolution of the system is obtained and the effect of the initial correlation on the time-evolution is examined in detail. (C) 2011 Elsevier B.V. All rights reserved.