This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The hidden world of quantum mechanics exists at scales many orders of magnitude smaller than living organisms, yet scientists have long theorized that quantum effects play an important role in biology. Birds' ability to sense magnetic fields during migration is one of the best-known mysteries in this field, with leading theories suggesting that this sensing could be achieved by exploiting quantum entanglement.
By proving a mathematical principle about how best to control quantum systems, researchers at the Okinawa Institute of Science and Technology (OIST) have taken what could be the penultimate step toward finally putting this avian hypothesis to the test, while also unlocking new biological platforms for quantum computing. Their results are published in the journal Quantum. Ugur Abdulla, head of the Analysis and Partial Differential Equations Unit at OIST, explains, "Many researchers have studied quantum effects and their role in biology, though it isn't always easy to translate an idea or hypothesis into a laboratory experiment.
We hope that by laying the mathematical foundation for controlling quantum phenomena, we can bring some of these ideas from quantum biology out of the theoretical realm and into the lab." Answering questions about quantum biology is no easy task. "Quantum effects are only relevant at tiny scales, much smaller than the macroscopic size of organisms. These interactions also happen incredibly fast and are notoriously difficult to pin down even in the most advanced experiments," Abdulla says.
Despite the quantum hypothesis of avian magnetoreception being proposed nearly 50 years ago, there has yet to be conclusive experimental evidence for or against it. The hypothesis of magnetoreception focuses on the idea that the speed of a biochemical reaction can depend on an external magnetic field. Biochemical reactions are all about rearranging electrons to form bonds, though even unbound, or "radical," pairs of electrons can become entangled and interact with each other via their magnetic properties encoded in quantum spin.
Whether these magnetic fields within a radical pair point in opposite or the same direction affects the coherence of the states and the speed at which stable bonds are formed. External magnetic fields, even weak ones, can influence how coherent a state is, meaning birds could theoretically use the concentration of product from a biochemical reaction to perceive Earth's magnetic field. Understanding how a magnetic field can be used to control a quantum system, whether for a bird's navigation or a quantum computing algorithm, falls under the study of quantum optimal control theory.
"The problem we're dealing with here is how you bring a quantum system from one state to another by using external control. This is the key problem in developing any new quantum technology, and is central to understanding quantum biology," Abdulla says. Abdulla and colleagues have previously proven the Pontryagin Maximum Principle (PMP) for spins in a magnetic field, which states that to create a maximally coherent state, one should use a "bang-bang optimization" approach, where the applied magnetic field abruptly switches between extreme values.
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