Imagine driving across the United States without a map or GPS. How would you do it? How would you know where you are and how far you had to go? As impossible as this feat seems, millions of birds perform it every year. Traversing thousands of miles on annual migrations, Arctic terns, bar-tailed godwits, and ruby-throated hummingbirds seem to know exactly where they are going, yet for years scientists had no idea how they did it. One physicist, Klaus Schulten, thought one explanation might be that the birds could sense the Earth’s magnetic fields, perhaps using magnetite molecules in their eyes. But no one knew how that was possible.
Recent research may provide a clue. Scientists now have evidence suggesting that at least some birds use quantum mechanics, the weird rules that govern the behavior of the microscopic world. A 2004 experiment involving robins showed that an extremely weak magnetic field could throw off the birds’ navigation abilities, an effect that made no sense if magnetite molecules provided the guidance, but fit perfectly with a model involving quantum entanglement, a subatomic process that allows widely separated objects to influence each other. In this model, when a photon of light enters a bird’s eye, it pops an electron out of a molecule called a cryptochrome. Since that electron is entangled with another electron still inside the molecule, the bird can compare the effect of the Earth’s magnetic field on them both. The slight differences could clue the bird in to the variations of magnetic fields, sort of like how having two eyes set slightly apart helps animals—including humans—navigate the world around them by sight.
Understanding the quantum mechanics of bird navigation may help the development of quantum computing, making computers vastly faster than they are today. While in today’s computers a transistor can store a bit as either a 1 or a 0 – on or off, in effect – a quantum bit, or qubit, can be in two states at once. The difference between today’s computers and quantum computers would be enormous. For instance, a quantum computer with 250 qubits would contain more bits than there are particles in the universe. And though progress in this field is slow, it is happening: Researchers at IBM’s Watson Research Center in Yorktown, NY, claimed in February that they had made significant advances in the performance of superconducting qubits.
You can learn more about this strange world by watching Quantum Biology: The Hidden Nature of Nature. Join journalist John Hockenberry as he moderates a discussion with cosmologist Paul Davies, engineer Seth Lloyd, and physicist Thorsten Ritz.