  By decomposing the important sampled imaginary time Schr\"odinger evolution
operator to fourth order with positive coefficients, we derived a number of
distinct fourth order Diffusion Monte Carlo algorithms. These sophisticated
algorithms require higher derivatives of the drift velocity and local energy
and are more complicated to program. However, they allowed very large time
steps to be used, converged faster with lesser correlations, and virtually
eliminated the step size error. We demonstrated the effectiveness of these
quartic algorithms by solving for the ground state properties of bulk liquid
helium.
