  Multi-orbital quantum impurity models with general interaction and
hybridization terms appear in a wide range of applications including embedding,
quantum transport, and nanoscience. However, most quantum impurity solvers are
restricted to a few impurity orbitals, discretized baths, diagonal
hybridizations, or density-density interactions. Here, we generalize the
inchworm quantum Monte Carlo method to the interaction expansion and explore
its application to typical single- and multi-orbital problems encountered in
investigations of impurity and lattice models. Our implementation generically
outperforms bare and bold-line quantum Monte Carlo algorithms in the
interaction expansion. So far, for the systems studied here, it remains
inferior to the more specialized hybridization expansion and auxiliary field
algorithms. The problem of convergence to unphysical fixed points, which
hampers so-called bold-line methods, is not encountered in inchworm Monte
Carlo.
