This study is motivated by the fact that low temperature coherence properties of quantum systems, crucial to quantum information processing, are typically determined by coupling to spin bath in solid state structures.

In collaboration with L. J. Sham, Renbao Liu and S. K. Saikin, we developed the quantum theory of decoherence and theory of coherence protection for quantum system in contact with a mesoscopic bath of slowly interacting spins. These theories are applied to one electron spin in a bath of many interacting nuclear spins in a semiconductor quantum dot, a paradigmatic system in mesoscopic physics and in spin-based quantum technology. The spin language can be easily generalized to a quantum object in contact with a bath of interacting multilevel quantum units. See [5], [7], [8] & [11] in publication list.