  We devise a framework based on the generalized contact formalism that
combines the nuclear shell model and quantum Monte Carlo methods and compute
the neutrinoless double-beta decay of experimentally relevant nuclei, including
$^{76}$Ge, $^{130}$Te, and $^{136}$Xe. In light nuclei, we validate our nuclear
matrix element calculations by comparing against accurate variational Monte
Carlo results. Due to additional correlations captured by quantum Monte Carlo
and introduced within the generalized contact formalism, in heavier systems, we
obtain long-range nuclear matrix elements that are about 30% smaller than
previous shell-model results. We also evaluate the recently recognized
short-range nuclear matrix element estimating its coupling by the
charge-independence-breaking term of the Argonne $v_{18}$ potential used in the
Monte Carlo calculations. Our results indicate an enhancement of the total
nuclear matrix element by around 30%.
