Fig. 1: Sampling the reduced density matrix in path-integral QMC.
From: Entanglement microscopy and tomography in many-body systems
Panel (a) shows the partition function in the space (r) - time (τ) manifold appearing in usual QMC simulations, with the periodic structure of imaginary time. Panel (b) shows how the RDM is sampled in such QMC simulations, where one imposes open boundary conditions in time for the skeletal sites in subregion A. From the QMC histogram of configurations of these sites, in this case, there will be 4 4 configurations for the 2 spins in A, and the corresponding matrix elements in the RDM are recorded. The lower panel in (b) demonstrates the spatial partition of A and B in such a setting.
