Studies of Short-Time Decoherence for Evaluation of Quantum Computer   Designs
  We review our recent results on short time approximations, with emphasis on applications for which the system-environment interactions involve a general non-Hermitian system operator and its conjugate. We evaluate the onset of decoherence at low temperatures in open quantum systems. The developed approach is complementary to Markovian approximations and appropriate for evaluation of quantum computing schemes. Example of a spin system coupled to a bosonic heat bath is discussed. 
Vladimir Privman, Denis Tolkunov