@article {1366, title = {Controlling a mesoscopic spin environment by quantum bit manipulation}, journal = {Physical Review Letters}, volume = {91}, year = {2003}, month = {2003/12/10}, abstract = {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 ({\textquoteleft}{\textquoteleft}dark states{\textquoteright}{\textquoteright}) 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. }, doi = {10.1103/PhysRevLett.91.246802}, url = {http://arxiv.org/abs/cond-mat/0308459v1}, author = {J. M. Taylor and A. Imamoglu and M. D. Lukin} }