Full Configuration Interaction Quantum Monte Carlo for Accurate $\mathit{\text{Ab}}\mathit{\text{Initio}}$ Nuclear Structure Calculations

We introduce novel full configuration interaction quantum Monte Carlo (FCIQMC) as an accurate many-body solver for $\mathit{\text{ab}}\mathit{\text{initio}}$ nuclear structure calculations. This stochastic approach directly samples the exact wave function in the full configuration space, enabling high-fidelity treatment of high-order many-body correlations in strongly interacting nuclear systems. Using interactions from chiral effective field theory, we have computed ground-state energies and charge radii of ${}^4$He, ${}^8$Be, ${}^{12}$C and ${}^{16}$O with sub-percent-level many-body uncertainties. These results establish FCIQMC as a stochastic full-configuration-space solver capable of treating systems beyond the reach of the conventional no-core shell model, and as an accurate benchmark for truncated many-body expansion methods.