



01129nas a2200145   4500008004100000245007400041210006900115260001500184490000700199520067900206100001900885700001700904700001800921856004400939       2003                        eng d00aControlling a mesoscopic spin environment by quantum bit manipulation0 aControlling a mesoscopic spin environment by quantum bit manipul  c2003/12/100 v913 aWe 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.
1 aTaylor, J., M.1 aImamoglu, A.1 aLukin, M., D.  uhttp://arxiv.org/abs/cond-mat/0308459v1