Performance analysis of continuous-time solvers for quantum impurity models

Impurity solvers play an essential role in the numerical investigation of strongly correlated electrons systems within the ``dynamical mean field'' approximation. Recently, a new class of continuous-time solvers has been developed based on a diagrammatic expansion of the partition function in either the interactions or the impurity-bath hybridization. We investigate the performance of these two complementary approaches and compare them to the well-established Hirsch-Fye method. The results show that the continuous-time methods, and, in particular, the version which expands in the hybridization, provide substantial gains in computational efficiency.