In-medium QCD forces at high temperature

We derive the quantum dynamics of heavy quark systems in quark-gluon plasma as open quantum systems. The scatterings of a heavy quark with the hard medium particles give rise to Debye screened QCD force and drag force and its fluctuation. We present a unified quantum description of these in-medium QCD forces at high temperature in the leading-order perturbation on the basis of the influence functional formalism.