Inchworm quasi Monte Carlo for quantum impurities

The inchworm expansion is a promising approach to solving strongly correlated quantum impurity models due to its reduction of the sign problem in real and imaginary time. We show that the imaginary time integration is amenable to quasi Monte Carlo, with enhanced N^-1 convergence, compared to standard inchworm Monte Carlo calculations with N^-1/2 convergence. This extends the applicability of the inchworm method to, e.g., multi-orbital Anderson impurity models with off-diagonal hybridization, relevant for materials simulation, where continuous time hybridization expansion Monte Carlo has a severe sign problem. We also present an open source implementation of our Inchworm quasi Monte Carlo approach: QInchworm.jl, implemented in the Julia programming language.