With standard sources of light photons do not normally interact with each other. This can be shown simply by shining two torches at the same spot. This means that the development from researchers based at the Massachusetts Institute of Technology and Harvard University, where photons have been made to interact, is a significant accomplishment. The outcome is a new type of photonic matter.
This has been demonstrated in recent studies. Scientists passed a weak laser beam through a dense cloud of ultra-cold rubidium atoms. As this happened the light did not exit the cloud in the form of a single, randomly spaced series of photons. Instead the photons were found to have bound together as pairs or triplets. This unusual event suggested some type of interaction (an attraction) taking place.
What appeared to happen was that the bound photons acquired a fraction of an electron’s mass. This meant the photons slowed down, traveling about 100,000 times slower than normal (photons normally travel, unsurprisingly, at the speed of light: 300,000 kilometers per second).
The significance of this, according to lead researcher Professor Vladan Vuletic in conversation with Laboratory Manager magazine, is if the photons can be made to interact in alternate ways, then the photons could be harnessed to execute very fast, incredibly complex quantum computations. Therefore, this altered form of light could play a major part in the development of quantum computers.
Linear Optical Quantum Computing, for example, uses photons as information carriers. This is as linear optical elements (including beam splitters, phase shifters, and mirrors) in order to process quantum information. This theoretical computer model could use photon detectors and quantum memories to detect and store quantum information.
Linking this type of machine to the research, Professor Vuletic explains: “Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers.”
He adds: “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.”
Going forward, the researchers intend to look for ways to coerce other interactions such as repulsion, where photons may scatter off each other like billiard balls. The new research has been published in the journal Science. The research paper is titled “Observation of three-photon bound states in a quantum nonlinear medium.”
