Ground and excited state energy calculations of the H2 molecule using a variational quantum eigensolver algorithm on an NMR quantum simulator

TL;DR

This paper demonstrates the use of a variational quantum eigensolver on an NMR quantum processor to calculate ground and excited state energies of the H2 molecule, including a novel single-qubit simulation approach.

Contribution

It introduces the first single-qubit simulation of H2 energy calculations and experimentally verifies variational quantum algorithms on an NMR quantum computer.

Findings

Single-qubit simulation accurately computes H2 energies.

Variational quantum eigensolver effectively finds ground states.

Excited states can be simulated with variational quantum deflation.

Abstract

Variational quantum algorithms are emerging as promising candidates for near-term practical applications of quantum information processors, in the field of quantum chemistry. We implement the variational quantum eigensolver algorithm to calculate the molecular ground-state energy of the H2 molecule and experimentally demonstrated it on an NMR quantum processor. Further, we simulate the excited states of the H2 molecule using the variational quantum deflation algorithm and experimentally demonstrate it on the same NMR quantum processor. We also develop the first simulation of the energy calculation of the H2 molecule using only a single qubit, and verify the results on an NMR quantum computer. Our experimental results demonstrate that only a single NMR qubit suffices to calculate the molecular energies of the H2 molecule to the desired accuracy.