  We develop the impurity lattice Monte Carlo formalism, for the case of two
distinguishable impurities in a bath of polarized fermions. The majority
particles are treated as explicit degrees of freedom, while the impurities are
described by worldlines. The latter serve as localized auxiliary fields, which
affect the majority particles. We apply the method to non-relativistic
three-dimensional systems of two impurities and a number of majority particles
where both the impurity-impurity interaction and the impurity-majority
interaction have zero range. We consider the case of an attractive
impurity-majority interaction, and we study the formation and disintegration of
bound states as a function of the impurity-impurity interaction strength. We
also discuss the potential applications of this formalism to other quantum
many-body systems.
