Hamiltonian Simulation of Quantum Beats in Radical Pairs Undergoing Thermal Relaxation on Near-term Quantum Computers

TL;DR

This paper demonstrates how near-term quantum computers can simulate quantum beats in radical pairs, including thermal relaxation, outperforming classical methods and highlighting their potential in quantum chemistry research.

Contribution

It introduces quantum simulation techniques for radical pair dynamics with thermal relaxation on near-term quantum hardware, incorporating noise models and experimental data comparison.

Findings

Quantum computers can simulate noisy quantum beats more accurately than classical methods.

Near-term quantum hardware matches experimental relaxation data over time.

Quantum simulation outperforms classical approximations in modeling open quantum systems.

Abstract

Quantum dynamics of the radical pair mechanism is a major driving force in quantum biology, materials science, and spin chemistry. The rich quantum physical underpinnings of the mechanism are determined by a coherent oscillation (quantum beats) between the singlet and triplet spin states and their interactions with the environment, which is challenging to experimentally explore and computationally simulate. In this work, we take advantage of quantum computers to simulate the Hamiltonian evolution and thermal relaxation of two radical pair systems undergoing the quantum-beat phenomena. We study radical pair systems with nontrivial hyperfine coupling interactions, namely, 9,10-octalin+/p-terphenyl-d14 and 2,3-dimethylbutane/p-terphenyl-d14 that have one and two groups of magnetically equivalent nuclei, respectively. Thermal relaxation dynamics in these systems are simulated using three methods: Kraus channel representations, noise models on Qiskit Aer and the inherent qubit noise present on the near-term quantum hardware. By leveraging the inherent qubit noise, we are able to simulate noisy quantum beats in the two radical pairs better than with any classical approximation or quantum simulator. While classical simulations of paramagnetic relaxation grow errors and uncertainties as a function of time, near-term quantum computers can match the experimental data throughout its time evolution, showcasing their unique suitability and future promise in simulating open quantum systems in chemistry.