  Inspired by the recent proposed Legendre orthogonal polynomial representation
of imaginary-time Green's functions, we develop an alternate representation for
the Green's functions of quantum impurity models and combine it with the
hybridization expansion continuous-time quantum Monte Carlo impurity solver.
This representation is based on the kernel polynomial method, which introduces
various integral kernels to filter fluctuations caused by the explicit
truncations of polynomial expansion series and improve the computational
precision significantly. As an illustration of the new representation, we
reexamine the imaginary-time Green's functions of single-band Hubbard model in
the framework of dynamical mean-field theory. The calculated results suggest
that with carefully chosen integral kernels the Gibbs oscillations found in
previous orthogonal polynomial representation have been suppressed vastly and
remarkable corrections to the measured Green's functions have been obtained.
