Multi-reference Trial State for Lattice Quantum Monte Carlo Simulations

TL;DR

This paper introduces a new sampling method for multi-reference trial states in nuclear lattice effective field theory, significantly improving the accuracy and efficiency of nuclear many-body simulations.

Contribution

It develops a novel sampling technique for incorporating multi-reference trial states into NLEFT, enhancing simulation precision for nuclear ground and excited states.

Findings

Improved energy calculations for $^7$Li and $^8$Li

Enhanced electromagnetic property predictions

More accurate transition probabilities

Abstract

Nuclear lattice effective field theory (NLEFT) is an efficient \textit{ab initio} tool for solving nuclear many-body systems using the imaginary-time projection technique, where the preparation of trial states is essential for substantially reducing the computational cost required to achieve the desired numerical precision. It has been challenging in forming optimal multi-reference trial states using multiple Slater determinants within auxiliary-field based quantum Monte Carlo frameworks like NLEFT. In this work, we develop a novel sampling method for efficiently incorporating such multi-reference trial states into NLEFT calculations. We applied the optimized trial state to $^7$Li and $^8$Li, finding overall improvements in calculated energies, electromagnetic properties, and transitions compared to results obtained without these optimizations. Our approach provides a reliable foundation for accurately simulating nuclear ground and low-lying excited states within the NLEFT framework.