Off-Diagonal Expansion Quantum Monte Carlo

Roger G. Melko

T. Mizusaki, Takaharu Otsuka, Michio Honma

Itay Hen, Tameem Albash

We study the performance of the Off-Diagonal Expansion quantum Monte Carlo algorithm on quantum spin glasses, specifically, 3-regular random antiferromagnets augmented with a transverse magnetic field. We demonstrate the advantages, sometimes by orders of magnitude, of the technique by comparing its runtimes against existing state-of-the-art schemes such as Path Integral quantum Monte Carlo and Stochastic Series Expansion.

Matthew Clifford Wilson

Malvin H. Kalos, G.A. Mikhailov

Hiroshi Shinaoka, Yusuke Nomura, Silke Biermann +2 more

The negative sign problem in quantum Monte Carlo (QMC) simulations of cluster impurity problems is the major bottleneck in cluster dynamical mean-field calculations. In this paper, we systematically investigate the dependence of the sign problem on the single-particle basis. We explore both the hybridization-expansion and interaction-expansion variants of continuous-time QMC simulations for three-site and four-site impurity models with baths that are diagonal in the orbital degrees of freedom. We find that the sign problem in these models can be substantially reduced by using a nontrivial single-particle basis. Such bases can be generated by diagonalizing a subset of the intracluster hoppings.