Non-Markovianity Hierarchy of Gaussian Processes and Quantum   Amplification
  We investigate dynamics of Gaussian states of continuous variable systems under Gaussianity preserving channels. We introduce a hierarchy of such evolutions encompassing Markovian, weakly and strongly non-Markovian processes, and provide simple criteria to distinguish between the classes, based on the degree of positivity of intermediate Gaussian maps. We classify all single-mode phase-insensitive Gaussian channels according to their non-Markovianity degree, and show that weak non-Markovianity has an operational significance as it leads to temporary amplification of Gaussian inputs beyond the fundamental quantum limit. Explicit examples and applications are discussed. 
Pietro Liuzzo-Scorpo, Wojciech Roga, Leonardo A. M. Souza, Nadja K.   Bernardes, Gerardo Adesso
quant-ph