  Amid the growing interest in non-Hermitian quantum systems, non-interacting
models have received the most attention. Here, through the stochastic series
expansion quantum Monte Carlo method, we investigate non-Hermitian physics in
interacting quantum systems, e.g., various non-Hermitian quantum spin chains.
While calculations yield consistent numerical results under open boundary
conditions, non-Hermitian quantum systems under periodic boundary conditions
observe an unusual concentration of imaginary-time worldlines over nontrivial
winding and require enhanced ergodicity between winding-number sectors for
proper convergences. Such nontrivial worldline winding is an emergent physical
phenomenon that also exists in other non-Hermitian models and analytical
approaches. Alongside the non-Hermitian skin effect and the point-gap
spectroscopy, it largely extends the identification and analysis of
non-Hermitian topological phenomena to quantum systems with interactions,
finite temperatures, biorthogonal basis, and periodic boundary conditions in a
novel and controlled fashion. Finally, we study the direct physical
implications of such nontrivial worldline winding, which bring additional,
potentially quasi-long-range contributions to the entanglement entropy.
