Have you ever wondered how birds instinctively find their way across thousands of miles of open sky during migration? Or pondered photosynthesis, or how the human sense of smell works?
Despite our best efforts to understand them, natural processes such as these are puzzling. But recently, scientists have been using quantum physics to unravel some of nature’s enduring mysteries.
The realm of quantum physics is, at times, bizarre and confusing. It contains a number of principles that defy logic; like quantum tunnelling, where a particle is able to penetrate ghostlike through a solid object.
Another strange feature of quantum physics is entanglement, which Albert Einstein famously called “spooky action at a distance”. This is when two particles form a connection across an unknown distance, which could be a millimetre or the width of a universe, and one of the particles can vanish from one area and reappear elsewhere.
This weird and wonderful world up-ends accepted scientific wisdom, creating obstacles to conventional thinking.
While entanglement may have appeared “spooky” to Einstein’s brilliant mind, subsequently the scientific community has grappled with that and other counterintuitive aspects of quantum physics.
Some have turned their backs on quantum theories that challenge accepted laws of physics.
But despite – or maybe because of – its unusual aspects, quantum physics is improving our understanding of the natural world, to a point where some of these theories can no longer be overlooked.
Quantum research has been selected by the World Economic Forum’s scientific community as one of the most important “future frontiers” in science.
And the emerging field of quantum biology could be the key to explaining the previously inexplicable.
A new study suggests living bacteria can be put into “quantum entanglement”. If bacteria are confirmed to exhibit quantum effects, it would form the first evidence of interplay between macroscopic organic matter and the subatomic quantum world.
What about photosynthesis?
A number of studies have linked a quantum reaction with the process of photosynthesis. Plant cells collect light particles, which release energy-gathering particles called excitons. The excitons carry the energy to the reaction centre, where it is turned into chemical energy and metabolized by the plant.
Everything happens in a billionth of a second to avoid losing heat, and with complete accuracy. Although the excitons don’t travel along one single path or another, energy still flowed in an instant to the reaction centre, but it wasn’t clear how.
In a 2007 experiment, biophysicist Greg Engel showed that excitons undergo a quantum reaction called superposition, where particles can exist in two places at once and in two states – a particle and a wave.
Engel, a professor at the University of Chicago and a World Economic Forum Young Scientist, found that excitons can travel as a wave and feel out all possible routes to the reaction centre, identifying the most efficient one to take.
He told Physics World: “The general notion that the language and mathematics of quantum information, including coherence, can be used to understand photosynthetic dynamics in ultrafast spectroscopy experiments seems to be growing in acceptance.”
So how do birds migrate?
Just as humans used compasses to find their way across open seas, birds navigate using an inner, chemical compass that picks up signals from the Earth’s magnetic field. As the signal is weak, scientists are unclear how it is picked up by birds.
University of Oxford researchers studied the migratory habits of the European robin. They suggest that when a photon of sunlight hits the robin’s retina, two unpaired electrons are released. Each electron spins to align itself with the Earth’s magnetic field and guides the bird towards warmer climates.
Another University of Oxford physicist, Simon Benjamin, suggests the process is the result of quantum entanglement, which could also explain how insects accurately orient themselves.
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Making sense of smells
Precisely how a human nose distinguishes the multitude of smells it encounters has eluded scientists. Molecules from the air enter the nostril and interact with receptors to determine one from another, but how this happens is unclear.
Chemist Luca Turin, of Alexander Fleming Biomedical Sciences Research Centre in Athens, suggests molecules contain electrons which arrive at the other side of the receptor in the nostril through quantum tunneling. Once through, the electron sends a signal to the brain to identify the smell, performing olfaction at the subatomic level.
Theoretical physicist, author and broadcaster Jim Al-Khalili likens the implausible phenomenon of quantum tunneling to throwing a tennis ball at a solid wall and it disappearing and reappearing at the other side.
In a TedGlobal London talk, he explained: “Quantum tunneling takes place all the time; in fact, it’s the reason our sun shines. The particles fuse together, and the Sun turns hydrogen into helium through quantum tunneling.”
In his talk, Al-Khalili recalled a quote from Danish physicist Niels Bohr, a pioneer in quantum mechanics, who said about the discipline: “If you're not astonished by it, then you haven't understood it.”