Increased coherence time in narrowed bath states in quantum dots
  We study the influence of narrowed distributions of the nuclear Overhauser field on the decoherence of a central electron spin in quantum dots. We describe the spin dynamics in quantum dots by the central spin model. We use analytic solutions for uniform couplings and the time dependent density-matrix renormalization group (tDMRG) for nonuniform couplings. With these tools we calculate the dynamics of the central spin for large baths of nuclear spins with or without external magnetic field applied to the central spin. The focus of our study is the influence of initial mixtures with narrowed distributions of the Overhauser field and of applied magnetic fields on the decoherence of the central spin. 
Lars B. Gravert, Peter Lorenz, Carsten Nase, Joachim Stolze, G\"otz S.   Uhrig
cond-mat.mes-hall quant-ph