It all started in 2013 when researchers from the Massachusetts Institute of Technology (MIT) and Harvard University observed pairs of photons -- particles of light -- interacting with each other and creating a new state of matter. Now, the same researchers have found that similar interactions can also take place in groups of three photons to eventually form a completely new kind of photonic matter that can be used in quantum computing, and perhaps even make sci-fi lightsabers a reality.
The newly created form of light can be explained by the example of lightsabers used in the imaginary universe of Star Wars. The photons in those fictional lightsaber beams would crash into each other, but photons in two normal light beams from flashlights would simply pass through each other, without making any interaction.
As part of their research, the scientists passed a weak laser beam through a thick cloud of cold rubidium atoms and managed to make the photons intermingle and bind together in pairs and in groups of three, instead of exiting the cloud as single randomly-spaced photons. The results clearly suggested that some kind of interaction was going on among the light particles.
Although the entire interaction within the atom cloud took place in just over a millionth of a second, the photons remained bound together, even after they traveled out of the cloud. This means that the photons were strongly entangled, which is considered to be a vital property for any quantum computing bit.
Unlike normal photons that do not have mass and travel at a speed of 300,000 kilometers per second, the entangled photons apparently acquired some mass, which was equivalent to a fraction of an electron's mass. These bound photons were also found to be relatively slow, traveling at a speed 100,000 times slower than that of normal photons.
The results, published in the journal Science on Friday, February 17, proved that photons could indeed attract each other. The researchers, therefore, believed that if photons can be made to interact in other ways, they may be harnessed to perform incredibly complex quantum computations extremely fast.
"Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers," MIT physics professor, Vladan Vuletic, said in a statement. "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."
The researchers now plan to look for ways to investigate other interactions such as repulsion, in which photons may scatter off each other like billiard balls.
"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," Vuletic said.