Quantum Coherence and Entanglement in the Avian Compass

TL;DR

This paper investigates the role of quantum entanglement in avian navigation, showing that entanglement persists long enough to be relevant but lacks directional sensitivity in natural geomagnetic fields, and proposes a new model with enhanced properties.

Contribution

It introduces a modified radical pair model with local magnetic fields that enhances entanglement duration and angular sensitivity, advancing understanding of quantum effects in bird navigation.

Findings

Entanglement lasts long enough for navigation relevance.

Birds cannot orient using radical-pair entanglement alone.

Modified model shows longer entanglement and angular sensitivity.

Abstract

The radical pair mechanism is one of two distinct mechanisms used to explain the navigation of birds in geomagnetic fields. However, little research has been done to explore the role of quantum entanglement in this mechanism. In this paper, we study the lifetime of radical pair entanglement corresponding to the magnitude and direction of magnetic fields to show that the entanglement lasts long enough in birds to be used for navigation. We also demonstrate that, due to a lack of orientational sensitivity of the entanglement in the geomagnetic field, the birds are not able to orient themselves by the mechanism based directly on radical-pair entanglement. To explore the entanglement mechanism further, we propose a model in which the hyperfine interactions are replaced by local magnetic fields of similar strength. The entanglement of the radical pair in this model lasts longer and displays an angular sensitivity in weak magnetic fields, both of these factors are not present in the previous models.