  Optical conductivity of graphene is studied using Quantum Monte Carlo
calculations. We start from Euclidean current-current correlator and extract
$\sigma (\omega)$ from Green-Kubo relations using Backus-Gilbert method.
Calculations were performed both for long-range interactions and taking into
account only contact term. In both cases we vary interaction strength and study
its influence on optical conductivity. We compare our results with previous
theoretical calculations choosing $\omega \approx \kappa$ thus working in the
region of the plateau in $\sigma(\omega)$ which corresponds to optical
conductivity of Dirac quasiparticles. No dependence of optical conductivity on
interaction strength is observed unless we approach antiferromagnetic phase
transition in case of artificially enhanced contact term. Our results strongly
support previous theoretical studies claimed very weak regularization of
graphene conductivity.
