The mystery of the quantum robin

Migratory songbirds have a remarkable "sixth sense" that allows them to use the Earth's magnetic field as a source of navigational information. This molecular compass is hypothesized to rely on the coherent spin dynamics of a radical pair of electrons, which are formed in the protein cryptochrome, located inside the animals' eyes. This remarkable, yet compelling, supposition relies on long-lived quantum coherences and entanglement, i.e. traits that are not typically associated with the wet, warm and noisy environment characteristic of living organisms.

Currently, the mechanism of magnetosensitivity is fiercely debated. While it has long been assumed that the process involves a light-induced reduction of the protein, this has failed to adequately explain sensitivity to weak geomagnetic fields. Instead, recent experiments point towards re-oxidation with molecular oxygen. This however raises new queries, as the associated radicals are subject to swift spin relaxation, which ought to abolish any magnetosensitivity. This project aims to resolve this debate and propose a new mechanism that relies on three radicals and the chemical Zeno effect. To this end, we will investigate the mysteries of cryptochrome magnetoreception, both by theoretical means (i.e. spin dynamic calculations based on the theory of open quantum systems) and by in vitro experiments, e.g. using time-resolved HDX-mass spectrometry to study the reoxidation of cryptochrome 4.