Researchers have found that a magnetically sensitive protein called Cryptochrome that mediates circadian rhythms in plants and animals helps birds to sense the earth's magnetic field and use it to navigate over long distances. Blue or green light triggers electrons in the protein to produce pairs of radicals whose electron spins respond to magnetic fields.
"As we vary the strength of the magnetic field, we can alter the progress of these photochemical reactions inside the protein," said Peter Hore, Physicist and lead researcher at University of Oxford.
Behavioural experiments have shown that even subtle disruptions to the magnetic field can impact the birds' ability to navigate. In a study led by Henrik Mouritsen, in collaboration with Hore, robins were placed in wooden huts on campus at the University of Oldenburg in Germany.
Without supplementary visual cues like the sun's position in the sky, the birds struggled to navigate. They regained their ability to orient only when the huts were covered in aluminium sheeting and electrically grounded, blocking external oscillating electromagnetic noise but not the earth's static magnetic field.
The behavioural findings in the field can inform the bird's molecular-level work in the laboratory. The electromagnetic noise has quantum-level effects on cryptochrome's performance.
The radical pairs in cryptochrome preserve their quantum coherence for much longer than previously believed possible. The finding may have broader implications for physicists hoping to extend coherence for more efficient quantum computing.
"Physicists are excited by the idea that quantum coherence could not just occur in a living cell, but could also have been optimized by evolution. There's a possibility that lessons could be learned about how to preserve coherence for long periods of time," Hore concluded.