Quantum Coherence and Sensitivity of Avian Magnetoreception

Abstract

Recently there has been growing interest in the application of quantum mechanics to understand many biological phenomena such as photosynthesis [1–7], the process of olfaction [8,9], enzymatic reactions [10,11], and avian magnetoreception [12–15]. These interests have brought physicists, chemists, and biologists to the same platform and led to the beginning of a new interdisciplinary subject called quantum biology [16,17]. A major motivation of these studies is to understand how nature utilizes purely quantum phenomena to optimize various biological processes. Here we are specifically interested in avian magnetoreception. It is very plausible that the navigation ability of some migratory birds is governed by the mechanism based on geomagnetic-dependent dynamics of spins of unpaired electrons in a radical pair. A recent theoretical study has estimated both the lifetime of the pair and the coherence time of this dynamics to be of the order of tens of microseconds [15]. The basic criterion used there postulates that bird’s navigation is disturbed if the signal produced by the dynamics is independent of the orientation of the geomagnetic field. This criterion together with the results of behavioral experiments in which European robins could not navigate in a weak oscillating magnetic field [18,19] led to the estimated life time and coherence time. Here we additionally take into account the results of other behavioral experiments in which the same species were observed to be temporarily disoriented in a constant magnetic field sufficiently stronger or weaker than the geomagnetic field [20,21]. We estimate the lifetime and coherence time of the order of several microseconds.