Because it’s been… days since we last discussed quantum entanglement, I think it’s time we broached the subject again.
Aren’t you excited, galleons? You should be.
Apparently, the eyes of migratory birds may preserve electrons in delicate quantum states for longer than the best artificial systems. Migratory birds use the Earth’s magnetic field to navigate, though their method vary (and, in fact, are poorly understood). One method (the important one for our talk today) may rely on light-triggered chemical changes determined by the bird’s orientation relative to Earth’s magnetic field.
This process is called the radical pair mechanism. And this is basically how it works:
Light excites two electrons in one molecule, sending one of them to another molecule. Inviting the neighbors to a party or something. Anyway, those two electrons, though no longer sharing the same molecular home, are entangled with one another. Eventually, the electrons will get off their light-high, calm down, and destroy this quantum bond. But before this happens, Earth’s magnetic field can alter the alignment of their spins, which alters the chemical properties of the molecules involved in the electron entanglement. By determining the concentrations of these chemicals on various parts of the eye, a bird can determine its orientation.
It’s like a tiny quantum compass.
Well, this whole idea made scientists wonder just how long these delicate quantum states could survive in the avian compass-eye. They decided to test this by exposing birds (in this case, European robins) to oscillating magnetic fields of varying strengths.
Essentially, they were trying to fuck with the radical pair mechanism. In the name of SCIENCE.
The tests revealed that a magnetic field of 15 nanoTesla, less than one-thousandth the strength of Earth’s magnetic field, was enough to interfere with a bird’s sense of direction. What’s so interesting about this is that the weaker an electromagnetic field is, the longer it takes to alter an electron’s spin. So, as a result of this experiment, scientists found that entanglement in a bird’s eye can last at least 100 microseconds.
Which might not sound terribly interesting, until you take into account the fact that the longest-lived entangled particles in an artificial system have only lasted a mere 80 microseconds.
“Nature has, for whatever reason, been able to protect quantum coherence better than we can do with molecules that have been specially designed,” says team member Simon Benjamin of the Centre for Quantum Technologies in Singapore.
Seems nature still has a few things to teach us. Kind of humbling, when you think about it.