Distance Bounds on Quantum Dynamics
  We derive rigorous upper bounds on the distance between quantum states in an open system setting, in terms of the operator norm between the Hamiltonians describing their evolution. We illustrate our results with an example taken from protection against decoherence using dynamical decoupling. 
D.A. Lidar, P. Zanardi, K. Khodjasteh (Center for Quantum Information   Science & Technology, USC)