Quantum simulation of molecules in solution

TL;DR

This paper extends the Variational Quantum Eigensolver to simulate molecules in solution using continuum models, demonstrating feasibility on noiseless and noisy quantum hardware with promising results.

Contribution

It introduces a method to incorporate solvation effects into quantum simulations without affecting algorithm efficiency, validated through simulations and hardware experiments.

Findings

Solvation effects do not hinder the VQE algorithm's efficiency.

Noiseless simulations with up to 12 qubits show accurate results.

Noisy hardware calculations yield fair solvation free energies.

Abstract

Quantum chemical calculations on quantum computers have been focused mostly on simulating molecules in gas-phase. Molecules in liquid solution are however most relevant for Chemistry. Continuum solvation models represent a good compromise between computational affordability and accuracy in describing solvation effects within a quantum chemical description of solute molecules. Here we report on the extension of the Variational Quantum Eigensolver to solvated systems, using the Polarizable Continuum Model. We show that accounting for solvation effects does not impact the algorithmic efficiency. Numerical results of noiseless simulations for molecular systems with up to twelve spin-orbitals (qubits) are presented. Furthermore, calculations performed on a simulated quantum hardware (IBM Q Mumbai), thus including noise, yield computed solvation free energies in fair agreement with the classical calculations without the inclusion of any error mitigation protocol.