Observations about utilitarian coherence in the avian compass

TL;DR

This study investigates the role of quantum coherence in the avian magnetic compass using complex radical pair models, revealing that global coherence correlates with compass sensitivity, emphasizing the importance of realistic modeling.

Contribution

It introduces large-scale radical pair models with up to 21 nuclear spins and identifies global coherence as a key factor in compass sensitivity, advancing understanding of quantum effects in biological systems.

Findings

Global coherence correlates with compass sensitivity

Electronic coherence alone is not a good predictor

Realistic models are crucial for understanding quantum biology

Abstract

It is hypothesised that the avian compass relies on spin dynamics in a recombining radical pair. Quantum coherence has been suggested as a resource to this process that nature may utilise to achieve increased compass sensitivity. To date, the true functional role of coherence in these natural systems has remained speculative, lacking insights from sufficiently complex models. Here, we investigate realistically large radical pair models with up to 21 nuclear spins, inspired by the putative magnetosensory protein cryptochrome. By varying relative radical orientations, we reveal correlations of several coherence measures with compass fidelity. Whilst electronic coherence is found to be an ineffective predictor of compass sensitivity, a robust correlation of compass sensitivity and a global coherence measure is established. The results demonstrate the importance of realistic models, and appropriate choice of coherence measure, in elucidating the quantum nature of the avian compass.