Exploiting the Variational Quantum Eigensolver for Determining Ground State Energy of Protocatechuic Acid

TL;DR

This study applies the Variational Quantum Eigensolver (VQE) to determine the ground state energy of protocatechuic acid, highlighting the importance of Ansatz choice and active space size for accuracy and convergence.

Contribution

It demonstrates the effectiveness of VQE with different Ansätze in calculating molecular energies and compares its performance to Hartree-Fock, emphasizing the impact of active space size.

Findings

VQE with UCCSD and Hardware-Efficient Ansätze achieves near-Hartree-Fock accuracy.

Increasing active space complicates convergence and accuracy.

VQE is a promising tool for molecular ground state energy analysis.

Abstract

The Variational Quantum Eigensolver (VQE) is a promising hybrid algorithm, utilizing both quantum and classical computers to obtain the ground state energy of molecules. In this context, this study applies VQE to investigate the ground state of protocatechuic acid, analyzing its performance with various Ans\"atze and active spaces. Subsequently, all VQE results were compared to those obtained with the Hartree-Fock (HF) method. The results demonstrate that Ans\"atze, like unitary coupled-cluster singles and doubles (UCCSD) and variations of Hardware-Efficient, generally achieve accuracy close to that of HF. Furthermore, the increase in active space has led to the models becoming more difficult to converge to values with a greater distance from the correct energy. In summary, the findings of this study reinforce the use of VQE as a powerful tool for analyzing molecular ground state energies. Finally, the results underscore the critical importance of Ansatz selection and active space size in VQE performance, providing valuable insights into its potential and limitations.