Chemically Aware Unitary Coupled Cluster with ab initio Calculations on System Model H1: A Refrigerant Chemicals Application

TL;DR

This paper introduces a chemically aware Unitary Coupled Cluster approach combined with symmetry verification techniques to optimize quantum circuit synthesis for chemical simulations, significantly reducing circuit depth and error on current quantum hardware.

Contribution

It presents a novel chemically informed UCC method integrated with symmetry verification, enabling more efficient quantum simulations of chemical systems on near-term devices.

Findings

Achieved 90% reduction in two-qubit gate count for CH4

Reduced relative error to 0.2% in electronic energy calculations

Demonstrated successful quantum simulations of chemical reactions

Abstract

Circuit depth reduction is of critical importance for quantum chemistry simulations on current and near term quantum computers. This issue is tackled by introducing a chemically aware strategy for the Unitary Coupled Cluster ansatz. The objective is to use the chemical description of a system to aid in the synthesis of a quantum circuit. We combine this approach with two flavours of Symmetry Verification for the reduction of experimental noise. These method enable the use of System Model H1 for a 6-qubit QSE (Quantum Subspace Expansion). We present (i) calculations to obtain CH4 optical spectra; (ii) an atmospheric gas reaction simulation involving $[$CH$^{\cdot}_3$--H--OH$^{\cdot}]^{\ddagger}$. Using our chemically aware UCC state-preparation strategy in tandem with state of the art symmetry verification methods, we improve device yield for CH4 at 6-qubits. This is demonstrated by a 90% improvement in two-qubit gate count and reduction in relative error to 0.2% for electronic energy calculated on System Model H1.