%0 Journal Article %J Physical Review Letters %D 2003 %T Controlling a mesoscopic spin environment by quantum bit manipulation %A J. M. Taylor %A A. Imamoglu %A M. D. Lukin %X We present a unified description of cooling and manipulation of a mesoscopic bath of nuclear spins via coupling to a single quantum system of electronic spin (quantum bit). We show that a bath cooled by the quantum bit rapidly saturates. Although the resulting saturated states of the spin bath (``dark states'') generally have low degrees of polarization and purity, their symmetry properties make them a valuable resource for the coherent manipulation of quantum bits. Specifically, we demonstrate that the dark states of nuclear ensembles can be used to coherently control the system-bath interaction and to provide a robust, long-lived quantum memory for qubit states. %B Physical Review Letters %V 91 %8 2003/12/10 %G eng %U http://arxiv.org/abs/cond-mat/0308459v1 %N 24 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.91.246802