Abstract

Finite temperature quantum Monte Carlo (QMC) is a class of numerical techniques used to estimate the properties of quantum systems in thermal equilibrium. In most QMC schemes, simple observables such as average energy, specific heat, and local expectation values can be measured. However, deriving estimators for arbitrary observables is generally not possible. In contrast, we demonstrate that within the permutation matrix representation (PMR) framework of QMC, formal estimators for arbitrary observables can always be derived.For models like the transverse-field Ising model (TFIM), we prove that these formal estimators should work in principle and show they work well in practice. Specifically, we successfully estimate non-local Pauli operators, two-point imaginary-time correlation functions of non-local Pauli operators, and integrated susceptibilities. Furthermore, for other models, we provide a sufficient …

Date

March 17, 2025

Authors

Nic Ezzell, Lev Y Barash, Itay Hen

Conference

SMT 2025