Real-time quantum Monte Carlo for the spin-boson model

The spin–boson model consists of a two-state system coupled to a bath of non-interacting harmonic modes. This fundamental, yet non-trivial model describes dissipation in a quantum system and can be mapped to an impurity coupled to interacting electron leads. Using the inchworm Monte Carlo algorithm we are able to precisely compute various nonequilibrium properties of the spin-boson model, such as the real-time evolution of the population difference between the two states at different temperatures, different forms of the bosonic bath spectrum, and different values of the spin-bath coupling, including the strong coupling regime. We also discuss how to calculate the heat current through the system coupled to two baths at different temperatures using full counting statistics.