  The heavy quark diffusion coefficient is encoded in the spectral functions of
the chromo-electric and the chromo-magnetic correlators, of which the latter
describes the T/M contribution. We study these correlators at two different
temperatures $T=1.5T_c$ and $T=10^4T_c$ in the deconfined phase of SU(3) gauge
theory. We use gradient flow for noise reduction. We perform both continuum and
zero flow time limits to extract the heavy quark diffusion coefficient. Our
results imply that the mass suppressed effects in the heavy quark diffusion
coefficient are 20% for bottom quarks and 34% for charm quark at $T=1.5T_c$.
