- Albert EinsteinThe work partly led to the forecast of what entanglement: the idea that two particles can remain connected across vast distances of space and time.
- Einstein found the idea absurd and "spooky", but has since been demonstrated with countless quantum physics experiments.
- No one had ever photographed entangled photons, however, until a research group recently did a high-tech laser experiment.
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The black and white photo above is not much to see. However, the spectral, eye-like forms illustrate a strange phenomenon that made Albert Einstein tremble to the point that he died incredulously that he could exist.
The image represents the first photograph of quantum entanglement, or the "spectral" coupling of particles.
"The image we were able to capture is an elegant demonstration of a fundamental property of nature, seen for the first time in the form of an image" Paul-Antoine Moreau, a physicist at the University of Glasgow, said in a press release.
Moreau led a team of researchers who managed to create the image, published by the group a study Friday in the journal Science Advances.
Entanglement Quantum 101
The quantum entanglement is the now well-documented idea that two tiny particles can be paired and separated while remaining intimately and instantly connected over vast distances.
According to the laws of physics, two particles can be entangled with a binary property or state, yes or no, like the spin or phase polarization. But that state remains confused – or in "overlap" – until a particle is measured. So at the exact time of the observation, even if the particles are separated by light years of space, the other particle assumes the opposite state of its twin.
To understand this concept, imagine that each twisted particle was a box containing a cat. The cat inside would be both alive and dead at the same time – that is, until someone opened one of the boxes. If the cat seen in a box was alive, then the cat in the other box should be dead (or vice versa).
Einstein thought about it effect similar to teleportation it was so absurd that he described it as "spooky action at a distance".
"Einstein could not accept it" J.C. Séamus Davis, a physicist at Cornell University who studied quantum mechanics, previously say Business Insider. "Essentially he went to his grave by not accepting it as a fact, but now he has been shown millions of times to work."
One of the last studies to prove it, published in February 2017, used 600 year old starlight to show that two particles could not "fool" at the time of entanglement and share a state before being measured.
How and why small particles can get caught does not make sense in the context of our daily life. At small scales, the universe seems to play with different rules, many of which are paradoxical and defy reason. In some quantum mechanical scenarios, for example, an effect does not always follow a cause; the effect can, in fact, happen before its cause occurs.
No one should be accused of being confused by quantum mechanics, said Davis, since "we didn't evolve to understand" the theory and its counterintuitive ramifications.
"But the math, the forecasts starting from the 20's, turned out to be correct," he said. "It is the most successful scientific theory in the human race".
In all these decades, however, no one has ever captured an image of tangled particles. This is what Moreau and his colleagues decided to do.
As the entanglement was photographed for the first time
Particles of light called photons can be trapped by a number of quantum properties. However, with their experiment, the researchers chose a property called phase. The photons came out of an ultraviolet laser beam, then passed through a special crystal known to catch the phase of some photons.
Subsequently, their experiment divided the ray into two equal "arms" with a beam separator or a semi-specialized glass. At this point, some of the photons that the crystal had entangled separated.
A photon arm has passed through a filter to limit the particles to one of the four phases (a phase filter "measures" the property of a photon effectively, so it would instantly cause its partner to rotate). So the photons came into a very sensitive camera capable of detecting single photons. The other arm led to a high-speed shooting device for the camera.
The camera sensor recorded information only when two entangled photons – each coming from a separate arm – arrived at their respective detectors simultaneously and with opposite phases. Over time, the researchers created a patterned image of the entangled photons that hit the camera.
The entangled photons that passed through the phase filter were expected to form four eye models, and this is exactly what the image showed.
The experiment is based on further evidence that what scared Einstein is real, but also that the tangled particles could be used in future imaging applications in science, said Moreau.