A semiclassical theory of the Ehrenfest-time dependence of quantum   transport in ballistic quantum dots
  We present a trajectory-based semiclassical calculation of the Ehrenfest-time dependence of the weak localization correction and the universal conductance fluctuations of a ballistic quantum dot with ideal point contacts. While the weak localization correction is proportional to exp(-tau_E/tau_D), where tau_E and tau_D are the dot's Ehrenfest time and dwell time, respectively, the variance of the conductance is found to be independent of tau_E. The latter is in agreement with numerical simulations of the quantum kicked rotator [Tworzydlo et al., Phys. Rev. B 69, 165318 (2004) and Jacquod and Sukhorukov, Phys. Rev. Lett. 92, 116801 (2004)]. 
Piet W. Brouwer and Saar Rahav