Quantum Implementation of Unitary Coupled Cluster for Simulating Molecular Electronic Structure

TL;DR

This paper demonstrates the first experimental implementation of the unitary coupled-cluster method on a quantum system, specifically a trapped ion, to simulate molecular electronic structures and overcome classical computational limitations.

Contribution

It provides the first experimental evidence that the unitary coupled-cluster ansatz can be reliably performed on a quantum system, enabling efficient molecular simulations.

Findings

Successful simulation of HeH+ electronic structure

Probing of ground and excited states energies

Simulation of bond dissociation non-perturbatively

Abstract

In classical computational chemistry, the coupled-cluster ansatz is one of the most commonly used $ab~initio$ methods, which is critically limited by its non-unitary nature. The unitary modification as an ideal solution to the problem is, however, extremely inefficient in classical conventional computation. Here, we provide the first experimental evidence that indeed the unitary version of the coupled cluster ansatz can be reliably performed in physical quantum system, a trapped ion system. We perform a simulation on the electronic structure of a molecular ion (HeH$^+$), where the ground-state energy surface curve is probed, energies of excited-states are studied and the bond-dissociation is simulated non-perturbatively. Our simulation takes advantages from quantum computation to overcome the intrinsic limitations in classical computation and our experimental results indicate that the method is promising for preparing molecular ground-states for quantum simulation.