By Vlatko Vedral
In the race to create the most powerful computer in the world, could it be that we’ve been pipped at the post by our feathered friends?
“Migration of Birds? It’s All About Quantum Computing, Stupid”
European robins are crafty little creatures. Each year they make a round trip from the cold Scandinavian Peninsula to the warm equatorial planes of Africa, a hazardous trip of about four thousand miles each way. Armed with only their internal sense of direction these diligent birds regularly make the journey without any fuss.
Magnets and compasses
When faced with a similar challenge, what do we humans do? I for one wouldn’t trust my sense of direction to get me to the local supermarket, let alone take on such an epic journey. Fortunately, Ferdinand Magellan (the late 15th-century Portuguese explorer) had the same problem – and solved it: he worked out what a useful addition a compass could be to your journey: he showed how the Earth’s magnetic field – to which the compass is sensitive – could be used as a stable reference system to circumnavigate the Earth. So now, when we start in Europe and use a compass to follow the southward direction of the Earth’s magnetic field, we are confident we will eventually find ourselves in Africa. But while a compass may guide us humans, it’s not at all clear how robins find their way so unerringly and consistently. Do they also have a kind of inbuilt compass? Interestingly, evidence suggests that there is some kind of internal guidance mechanism, but it is not of the type Magellan used.
How do the robins do it?
Wolfgang Wiltschko, a biologist at the University of Frankfurt, came up with the first piece of evidence of this internal guidance mechanism in the early 1970s. He caught robins on their flight path from Scandinavia to Africa and put them in different artificial magnetic fields to test their behavior. (Note to reader: no robins were injured or suffered any obvious side effects in the making of this experiment!) One of Wiltschko’s key insights was to interchange the direction of the North and South and then observe how the robins reacted to this. Much to his surprise, nothing happened! Robins simply did not notice the reversal of the magnetic field. This is very telling: if you did this swap with a compass, its needle would follow the external field, make a U-turn, and point in the opposite direction to its original one. The human traveller would be totally confused. But somehow, the robins proved to be impermeable to the change.
Where brains, eyes, light, and magnetism seem to connect
Wiltschko’s experiments went on to demonstrate that though robins cannot tell magnetic North from magnetic South, they are able to estimate the angle the magnetic field makes with Earth’s surface. And this is really all they needed in order to navigate themselves. In a separate experiment, Wiltschko covered robins’ eyes and discovered that simply by doing this they were unable to detect the magnetic field at all. He concluded that, without light, the robins cannot even ‘see’ the magnetic field, whereas of course a compass works perfectly well in the dark. This was a significant breakthrough in our understanding of the birds’ navigation mechanism. The now widely-accepted explanation to Wiltschko’s result was proposed by Thorsten Ritz of the University of Southern Florida. A physicist by training, Ritz has a strong interest in chemistry and (as it happens) an inordinate affection for migratory birds. Ritz believes that there is a molecule in the bird’s eye which absorbs visible light (hence the need for open eyes) and that an electron within the molecule is then excited by the absorption.
This is where the quantum physics bit comes in
The key, however, is that the excitation also causes the electron to become ‘super correlated’ with another electron in the same molecule. This super-correlation manifests itself in the form that whatever is happening to one electron somehow affects the other one — they have become inseparable ‘twins’. Given that each of these twinned electrons is under the influence of the earth’s magnetic field, the field can be adjusted to affect the relative degree of ‘super-correlation’. So by picking up on the relative degree of ‘super-correlation’ (and relating this to the variation in the magnetic field) the birds somehow form an image of the magnetic field in their mind, and then use this to orient and navigate themselves. As a physicist, Ritz already knew a great deal about this super-correlation phenomenon: it had been proven many times in quantum physics under the name of ‘quantum entanglement’, or just ‘entanglement’ for short. It is this very same entanglement that scientists are trying to exploit in order to build a new type of superfast quantum computers. In collaboration with Elisabeth Rieper of National University of Singapore, and Simon Benjamin, John Morton and Erik Gauger of University of Oxford, I recently decided to estimate how long it might take robins to use the excited electrons in their eye to determine the direction of the magnetic field (a kind of computation inside the bird’s eyes).
The robins got there first
Our very simple model suggests that the computation performed by these robins is more powerful (in the sense that entanglement lasts longer) than any similar quantum computation we can currently perform! They are basically streets ahead of us! If this is corroborated by further evidence its implications would be truly remarkable. For one, this would make quantum computation yet another technology discovered by Nature long before any of us humans thought it possible. While Nature continues to humble us, it also brings new hope: the realization of a large-scale usable quantum computer is possibly not as distant as we once thought. All we need to do is perhaps find a way of better replicating what already exists out there in the natural world.
Vlatko Vedral studied undergraduate theoretical physics at Imperial College London, where he also received a PhD for his work on ‘Quantum Information Theory of Entanglement’. He is Professor of Quantum Information Science at the University of Oxford, and has published more than 130 research papers and written two textbooks. His most recent book is Decoding Reality: The Universe as Quantum Information. This article is reposted with permission from the BBC Focus Magazine/Oxford University Press microsite.