Sustained Quantum Coherence and Entanglement in the Avian Compass

Abstract

In artificial systems, quantum superposition and entanglement typically decay rapidly unless cryogenic temperatures are used. Could life have evolved to exploit such delicate phenomena? Certain migratory birds have the ability to sense very subtle variations in Earth's magnetic field. Here we apply quantum information theory and the widely accepted "radical pair" model to analyze recent experimental observations of the avian compass. We find that superposition and entanglement are sustained in this living system for at least tens of microseconds, exceeding the durations achieved in the best comparable man-made molecular systems. This conclusion is starkly at variance with the view that life is too "warm and wet" for such quantum phenomena to endure.

Physics of life: The dawn of quantum biology

“…Entanglement is usually quite delicate at ambient temperatures, but the researchers calculate that it is maintained in the avian compass for at least tens of microseconds -much longer than is currently possible in any artificial molecular system 10 .…”

Magnetic sensitivity and entanglement dynamics of the chemical compass

“…We will show that the mechanism damping singlet-triplet coherence also damps any electron spin entanglement possibly present, as is well understood in precision measurements. In so doing, we will also show that the recently appeared entanglement considerations [12,13] are questionable, since these works have not taken into account the fundamental singlet-triplet decoherence process. Finally, we will compare the three different and currently competing master equations attempting to describe the quantum dynamics of radical-ion-pair reactions.…”

“…The absence of this physical mechanism from the fundamental theoretical description of RP reactions leads to unphysical coherence and entanglement dynamics, and in their turn, these lead to violation of fundamental quantum limits. Furthermore, the entanglement considerations of Vedral and coworkers [13] are also based on the traditional theory, as the authors themselves state, rendering their qualitative and quantitative conclusions questionable.…”

“…For example, quantum coherence has been shown to play a fundamental role in photosynthesis [1][2][3][4][5][6][7][8], while quantum measurement dynamics have been demonstrated to underlie radical-ionpair reactions [9][10][11], the spin-dependent biochemical reactions at the heart of the avian magnetic compass mechanism. Even electron spin entanglement has also been addressed with respect to the chemical compass [12,13], paving the way for the dawn of quantum biology [14].…”

The quantum needle of the avian magnetic compass

“…In support of this proposal, the photochemistry of isolated cryptochromes in vitro has been found to respond to applied magnetic fields in a manner that is quantitatively consistent with the radical pair mechanism (15). Aspects of the radical pair hypothesis have also been explored in a number of theoretical studies, the majority of which have concentrated on the magnitude of the anisotropic magnetic field effect (9,10,16,17,(19)(20)(21)(22)(23)(24)(25)(26)(27). Very little attention has been devoted to the matter we address here: the precision of the compass bearing available from a radical pair sensor (28).…”