This stunning image captured last year by physicists at the University of Glasgow in Scotland is the first photo of quantum entanglement, a phenomenon so bizarre that physicist Albert Einstein described it as a “ creepy action at a distance. ”
It may not sound like much, but just stop and think for a second: This fuzzy gray image was the first time we saw the interaction of particles that underpins the strange science of quantum mechanics and forms the basis of quantum computing.
Quantum entanglement occurs when two particles are inextricably linked, and what happens to one immediately affects the other, regardless of how far apart they are. Hence the description of ‘creepy action at a distance’.
This particular photo shows the entanglement between two photons, two light particles. They are interacting and, for a brief moment, sharing physical states.
Paul-Antoine Moreau, first author of the article in which the image was revealed in July 2019, told the BBC that the image was “an elegant demonstration of a fundamental property of nature.”
To capture the incredible photo, Moreau and a team of physicists created a system that removed entangled photon currents in what they described as “unconventional objects.”
The experiment actually involved capturing four images of the photons at four different phase transitions. You can see the full image below:
(Moreau et al. Scientific advances, 2019)
What you’re looking at here is actually a composite of multiple images of the photons as they go through a series of four-phase transitions.
Physicists split the entangled photons and ran a beam through a liquid crystal material known as β-barium borate, triggering four-phase transitions.
At the same time, they captured photos of the tangled pair going through the same phase transitions, even though it had not passed through the liquid crystal.
You can see the setting below: the interlaced photon beam comes from the bottom left, half of the interlaced pair splits to the left, and passes through the four-phase filters. The others who go ahead did not go through the filters, but experienced the same phase changes.
(Moreau et al., Progress of science, 2019)
The camera was able to capture images of these at the same time, showing that they had both changed in the same way despite being divided. In other words, they were tangled.
While Einstein made quantum entanglement famous, the late physicist John Stewart Bell helped define quantum entanglement and established a test known as ‘Bell inequality’. Basically, if you can break the Bell inequality, you can confirm the true quantum entanglement.
“Here, we report an experiment demonstrating the violation of a Bell inequality in the observed images,” the team wrote in Scientific advances.
“This result opens the way to new quantum imaging schemes … and suggests promise for spatial variable-based quantum information schemes.”
The research was published in Progress of science.
A version of this article was first published in July 2019.
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