Quantum coherence and sensitivity of avian magnetoreception

Area of Science:

• Ornithology
• Biophysics
• Quantum Biology

Background:

• Migratory birds and other species possess the remarkable ability to navigate using the Earth's geomagnetic field.
• This navigation is thought to involve a quantum biological mechanism within the bird's eye, specifically utilizing radical pairs with unpaired electron spins.
• The geomagnetic field influences the spin dynamics of these radical pairs, forming the basis of the avian compass.

Purpose of the Study:

• To determine the average lifetime of radical pairs involved in avian magnetoreception.
• To investigate the role of environmental noise in the sensitivity of the avian navigation system.
• To reconcile experimental findings with theoretical models of radical pair mechanisms in cryptochromes.

Main Methods:

• Analysis of behavioral experiments conducted on European robins.
• Estimation of radical pair lifetimes based on observed navigation behaviors.
• Modeling the influence of environmental noise on radical pair spin dynamics.

Main Results:

• The estimated average lifetime of the radical pair is approximately one microsecond, consistent with experimental values for cryptochrome.
• A specific parameter regime was identified where environmental noise enhances the sensitivity of the avian compass.
• Contrary to expectations, long radical pair coherence times were found not to be essential and could potentially impair navigation.

Conclusions:

• The findings support the radical pair mechanism, involving cryptochromes, as the basis for avian magnetoreception.
• The study demonstrates that the avian compass can function effectively with a microsecond radical pair lifetime.
• Environmental noise plays a crucial, potentially enhancing, role in avian navigation sensitivity, challenging the necessity of long quantum coherence times.