IIT Bombay: Bird’s eye view and quantum biology

Migrating long distances, guided by a biological compass

While there have been theories about the way migratory birds navigate across the earth, these have not be placed on a firm footing. Now, a group from IIT Bombay has tied this theory with observed features of the birds’ biological compass to get a clear picture of how it works. They affirm that it is due to the interplay of chemical reactions, electron spins and the magnetic fields present. Thus, understanding the avian compass is a lesson in quantum biology. This may be of use, one day, in engineering quantum computers.

Migratory birds have biological sensors that can sense the earth’s magnetic field, and guide them in their long journeys spanning continents. One might, mistakenly assume that these sensors would be located in the brain. Contrarily, they are located in the eyes, more specifically, in the right eye, as studies on the European Robin reveal. The “compass” in question is generated by an interplay of the electron and nuclear “spins.”

The spins we talk about here are not to be understood in the conventional way, such as that of a rotating cricket ball. Spin is a name given to the quantum mechanical properties of these particles that can interact with magnetic fields.

Swaroop Ganguly, Department of Electrical Engineering, IIT Bombay, and collaborators have put the theory that the avian compass involves the interplay of electron spins and nuclear spins on a firm footing. They have shown that all observed characteristics of the avian compass can be explained thus. Their work is to be published in Physical Review E.

“If nature is indeed able to harness quantum spins in avian compass, understanding how [it works] might afford useful lessons to us in engineering quantum mechanical systems, such as sensing or computing hardware that is incomparably more powerful than what we have today,” says Dr Ganguly in an email to this correspondent.

Limiting window

A curious feature of the avian compass is that it has a sensitivity that peaks at values matching with the earth’s magnetic field. Just like humans have a “window” or range of frequencies limiting what they can hear, this leaves a window of magnetic field values the bird is sensitive to. The research has shown that it is the interaction between spins that naturally leads to this “functional window.”

There are many directions to take this further: Vishvendra Poonia, the first author of the paper, says: “One is to study the physics of biological systems, especially, the quantum effects in these systems. Secondly, and more importantly, [to] translate the knowledge gained from these biological systems into technological application, [namely] bio-inspired quantum technologies.”

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