  We use different numerical approaches to calculate the double occupancy and
mag- netic susceptibility as a function of a bias voltage in an Anderson
impurity model. Specifically, we compare results from the Matsubara-voltage
quantum Monte-Carlo approach (MV-QMC), the scattering-states numerical
renormalization group (SNRG), and real-time quantum Monte-Carlo (RT-QMC),
covering Coulomb repulsions ranging from the weak-coupling well into the
strong- coupling regime. We observe a distinctly different behavior of the
double occupancy and the magnetic response. The former measures charge
fluctuations and thus only indirectly exhibits the Kondo scale, while the
latter exhibits structures on the scale of the equilibrium Kondo tempera- ture.
The Matsubara-voltage approach and the scattering-states numerical
renormalization group yield consistent values for the magnetic susceptibility
in the Kondo limit. On the other hand, all three numerical methods produce
different results for the behavior of charge fluctuations in strongly
interacting dots out of equilibrium.
