Non-Markovianity and System-Environment Correlations in a microscopic   collision model
  We show that the use of a recently proposed iterative collision model with inter-environment swaps displays a signature of strongly non-Markovian dynamics that is highly dependent on the establishment of system-environment correlations. Two models are investigated; one in which such correlations are cancelled iteratively and one in which they are kept all across the dynamics. The degree of non-Markovianity, quantified using a measure based on the trace distance, is found to be much greater for all coupling strengths, when system-environment correlations are maintained. 
Ruari McCloskey and Mauro Paternostro
quant-ph