Analog Quantum Simulation of Coupled Electron-Nuclear Dynamics in Molecules

TL;DR

This paper introduces a novel analog quantum simulation method for coupled electron-nuclear molecular dynamics that operates without the Born-Oppenheimer approximation, offering exponential resource savings and suitability for near-term quantum devices.

Contribution

It presents the first pre-BO framework for molecular vibronic dynamics using an analog mapping of nuclear degrees of freedom onto qubits and bosonic modes.

Findings

Demonstrated a proof-of-principle emulation with a single-mode model.

Showed exponential resource savings over classical algorithms.

Proposed implementation on trapped-ion quantum devices.

Abstract

Quantum computing has the potential to reduce the computational cost required for quantum dynamics simulations. However, existing quantum algorithms for coupled electron-nuclear dynamics simulation either require fault-tolerant devices, or involve the Born-Oppenheimer (BO) approximation and pre-calculation of electronic states on classical computers. We present the first quantum simulation approach for molecular vibronic dynamics in a pre-BO framework with an analog mapping of nuclear degrees of freedom, i.e. without the separation of electrons and nuclei, by mapping the molecular Hamiltonian to a device with coupled qubits and bosonic modes. We perform a proof-of-principle emulation of our ansatz using a single-mode model system which represents vibronic dynamics of chemical systems, such as nonadiabatic charge transfer involving polarization of the medium, and propose an implementation of our approach on a trapped-ion device. We show that our approach has exponential savings in resource and computational costs compared to the equivalent classical algorithms. Furthermore, our approach has a much smaller resource and implementation scaling than the existing pre-BO quantum algorithms for chemical dynamics. The low cost of our approach will enable an exact treatment of electron-nuclear dynamics on near-term quantum devices.