Excitations of Quantum Many-Body Systems via Purified Ensembles: A Unitary-Coupled-Cluster-based Approach

TL;DR

This paper introduces a unified method combining state-average and individual state calculations for quantum many-body excitations using a purified ensemble approach based on unitary-coupled-cluster theory, with implications for electronic structure and quantum computing.

Contribution

It presents a novel approach that merges state-average and single-state methods into one framework using purified ensembles and unitary-coupled-cluster theory.

Findings

The method effectively handles multiple excitations in quantum systems.

Implications for electronic structure calculations are discussed.

Potential applications in quantum computing are highlighted.

Abstract

State-average calculations based on mixture of states are increasingly being exploited across chemistry and physics as versatile procedures for addressing excitations of quantum many-body systems. If not too many states should need to be addressed, calculations performed on individual states is also a common option. Here we show how the two approaches can be merged into one method, dealing with a generalized yet single pure state. Implications in electronic structure calculations are discussed and for quantum computations are pointed out.