Quantum versus classical hyperfine-induced dynamics in a quantum dot
  In this article we analyze spin dynamics for electrons confined to semiconductor quantum dots due to the contact hyperfine interaction. We compare mean-field (classical) evolution of an electron spin in the presence of a nuclear field with the exact quantum evolution for the special case of uniform hyperfine coupling constants. We find that (in this special case) the zero-magnetic-field dynamics due to the mean-field approximation and quantum evolution are similar. However, in a finite magnetic field, the quantum and classical solutions agree only up to a certain time scale t<\tau_c, after which they differ markedly. 
W. A. Coish, E. A. Yuzbashyan, B. L. Altshuler, and Daniel Loss