The Sign Problem in Density Matrix Quantum Monte Carlo.

ABSTRACT: Density matrix quantum Monte Carlo (DMQMC) is a recently developed method for stochastically sampling the N-particle thermal density matrix to obtain exact-on-average energies for model and ab initio systems. We report a systematic numerical study of the sign problem in DMQMC based on simulations of atomic and molecular systems. In DMQMC, the density matrix is written in an outer product basis of Slater determinants. In principle, this means that DMQMC needs to sample a space that scales in the system size, N, as O[(exp(N))²]. In practice, removing the sign problem requires a total walker population that exceeds a system-dependent critical walker population (N_c), imposing limitations on both storage and compute time. We establish that N

SUBMITTER: Petras HR 

PROVIDER: S-EPMC8515812 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature