“Crystals of light” may become a reality

17th February, 2018: In a combined effort of researchers from the Massachusetts Institute of Technology (MIT), Harvard University, University of Maryland, Princeton University and the University of Chicago has brought out the possibility of photons (particles of light) to combine to form a triplet, for the first time in the history of science. The result is reported in the journal, Science.

The observation goes against the contemporary belief that individual photons that make up light do not interact. In the experiment with ultra-cooled Rubidium (cooled up to a millionth of a degree above absolute zero), the researchers found that groups of three photons interacting and, in effect, sticking together to form a completely new kind of photonic matter.

It is well known that cooling the atoms slows them to a near standstill. Researchers allowed shine a very weak laser beam to pass through this cloud of immobilized atoms, such that only a handful of photons travel through the cloud at any one time. As they measured measure the photons as they come out the other side of the atom cloud, they found that the photons streamed out as pairs and triplets.

Now, the photons that have interacted with each other, in this case through an attraction between them, can be thought of as strongly correlated, or entangled. Such entanglement is considered a key property for any quantum computing bit.

“If photons can influence one another, then if you can entangle these photons, and we’ve done that, you can use them to distribute quantum information in an interesting and useful way,” comments the researchers.

It’s completely novel in the sense that we don’t even know sometimes qualitatively what to expect,” Vuletic, the principal author of the paper reports. “With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light? Or will something else happen? It’s very uncharted territory.