Physicists have obtained an image of a strong form of quantum entanglement called Bell's entanglement, visual evidence of what Albert Einstein once called 'spooky action at a distance'.
Two particles that interact with each other, as two photons that pass through a beam splitter, for example, can remain connected, instantly sharing their physical states no matter how large the distance that separates them. This connection is known as quantum entanglement, and supports the field of quantum mechanics.
Einstein thought that quantum mechanics was 'creepy' because of the snapshot of the apparent remote interaction between two intertwined particles, which seemed incompatible with the elements of his special theory of relativity.
Later, Sir John Bell formalized this concept of nonlocal interaction that describes a strong form of entanglement that exhibits this satin 'spooky'. At present, although Bell's entanglement is exploited in practical applications such as quantum computing and cryptography, it has never been captured in a single image.
In an article published in the journal Science Advances, a team of physicists from the University of Glasgow describes how they have done the fear of Einstein is visible in an image for the first time.
They devised a system that triggers a stream of intertwined photons from a quantum light source towards "unconventional objects", which are shown in liquid crystal materials that change the phase of the photons as they pass.
They installed a super sensitive camera capable of detecting individual photons that would only take an image when they saw a photon and its "twin" interlaced, creating a visible record of the entanglement of photons.
Paul-Antoine Moreau of the School of Physics and Astronomy of the University of Glasgow is the main author of the article. Moreau said: "The image that we have managed to capture is a elegant demonstration of a fundamental property of nature, first seen in the form of an image.
"It's an exciting result that could be used to advance the emerging field of quantum computing and lead to new types of images," he added.