The preparation of states in quantum mechanics

The important problem of how to prepare a quantum mechanical system, S, in a specific initial state of interest-e.g., for the purposes of some experiment-is addressed. Three distinct methods of state preparation are described. One of these methods has the attractive feature that it enables one to prepare S in a preassigned initial state with certainty, i.e., the probability of success in preparing S in a given state is unity. This method relies on coupling S to an open quantum-mechanical environment, E, in such a way that the dynamics of S boolean OR E pulls the state of S towards an "attractor," which is the desired initial state of S. This method is analyzed in detail. (C) 2016 AIP Publishing LLC.