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oct07-offprint-ghose.pdf

 We discuss the quantum to classical transition  as a consequence of entanglement of a quantum  system with an environment or a detector. Our  discussion focuses on the effect of continuous  measurement on the system dynamics. We  review recent research showing how to model  weak continuous measurements as nonlinear  dynamical evolutions within the quantum trajectory  formalism, and establish a set of necessary  quantitative conditions for the quantum to  classical transition to take place. This analysis is  extended to a bipartite open quantum system,  with a spin coupled to a harmonic oscillator as  a specific example, to show that classical  dynamics emerges despite the persistence of  entanglement in the classical limit.