2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/136458We 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)].14 pages, 9 figures; Substantially revised manuscript, correcting mistakes in earlier versionsMesoscale and Nanoscale Physicstext