Capturing many-body correlation effects with quantum and classical computing

TL;DR

This paper explores how quantum computing, specifically Quantum Phase Estimator, can efficiently identify core-level states in molecular systems, potentially surpassing classical methods in handling complex many-body correlations.

Contribution

The study demonstrates the effectiveness of Quantum Phase Estimator in capturing many-body correlation effects in molecular excited states, validated against established classical methods.

Findings

QPE accurately identifies core-level states relevant to x-ray photoelectron spectroscopy.

QPE shows potential to reduce computational overhead compared to classical methods.

Validation against exact diagonalization confirms QPE's reliability.

Abstract

Theoretical descriptions of excited states of molecular systems in high-energy regimes are crucial for supporting and driving many experimental efforts at light source facilities. However, capturing their complicated correlation effects requires formalisms that provide a hierarchical infrastructure of approximations. These approximations lead to an increased overhead in classical computing methods, and therefore, decisions regarding the ranking of approximations and the quality of results must be made on purely numerical grounds. The emergence of quantum computing methods has the potential to change this situation. In this study, we demonstrate the efficiency of Quantum Phase Estimator (QPE) in identifying core-level states relevant to x-ray photoelectron spectroscopy. We compare and validate the QPE predictions with exact diagonalization and real-time equation-of-motion coupled cluster formulations, which are some of the most accurate methods for states dominated by collective correlation effects.