Krylov-projected quantum Monte Carlo

TL;DR

This paper introduces a novel quantum Monte Carlo method that uses Krylov subspace projections to accurately compute spectral, thermal, and excited state properties without analytic continuation, applicable to various models and systems.

Contribution

It presents an unbiased Krylov projection approach within quantum Monte Carlo for calculating diverse quantum properties, avoiding the need for analytic continuation.

Findings

Successfully computed temperature-dependent properties for Hubbard models

Calculated spectral functions and excited states in ab initio systems

Demonstrated accuracy and versatility of the method

Abstract

We present an approach to the calculation of arbitrary spectral, thermal and excited state properties within the full configuration interaction quantum Monte Carlo framework. This is achieved via an unbiased projection of the Hamiltonian eigenvalue problem into a space of stochastically sampled Krylov vectors, thus enabling the calculation of real-frequency spectral and thermal properties and avoiding explicit analytic continuation. We use this approach to calculate temperature-dependent properties and one- and two-body spectral functions for various Hubbard models, as well as isolated excited states in ab initio systems.