  The relativistic diffusion process of heavy quarks is formulated on the basis
of the relativistic Langevin equation in It\^{o} discretization scheme. The
drag force inside the quark-gluon plasma (QGP) is parametrized according to the
formula for the strongly coupled plasma obtained by the AdS/CFT correspondence.
The diffusion dynamics of charm and bottom quarks in QGP is described by
combining the Langevin simulation under the background matter described by the
relativistic hydrodynamics. Theoretical calculations of the nuclear
modification factor R_{AA} and the elliptic flow v_{2} for the single electrons
from the charm and bottom decays are compared with the experimental data from
the relativistic heavy ion collisions. The R_{AA} for electrons with large
transverse momentum (p_{T} > 3 GeV) indicates that the drag force from the QGP
is as strong as the AdS/CFT prediction.
