If you turn on two flashlights and cross their rays, nothing much will happen. The reason is that photons do not interact with each other. But what if it was not so, and the particles of light could attract and repel each other like ordinary atoms? Perhaps, in this case, the rays of light, meeting, would strengthen each other and merge into a single luminous flux. It seems empty fantasies, the implementation of which is impossible under the existing laws of physics. However, scientists from the Massachusetts Institute of Technology made photons interact. In their experiment, described by Science Daily, the three light particles stuck together, forming an entirely new kind of light. The first successful experiments took place in 2013, when the interaction of a pair of photons. In the new work, scientists are interested in whether it is possible to bind three or more light particles. To do this, they missed a very weak laser beam through a dense cloud of ultracold atoms of rubidium. At the output, the photons were combined into pairs and triplets. Unlike free photons, which do not have mass and move at a speed of 300,000 km / s, these structures acquired a mass fraction of the electron and slowed down approximately 100,000 times. To explain the phenomenon, a special physical model was developed. According to the authors, traveling through a dense rubidium cloud, a few photons jump from one atom to another. Thus they become so-called polaritons - half photons, half atoms. Polaritons are able to interact, connecting through their atomic constituents. At the exit from the cloud, the polaritons again become photons, but they remain connected. We can say that photons "remember" what happened to them inside the cloud. Related photons can be considered as intricate, which allows them to be used for communication, for example, in optical fibers. This opens up new opportunities for the dissemination of information and quantum computing. The team hopes to be able to discover other interesting interactions of photons - for example, repulsion or even the formation of correct patterns or crystals.

The physicists from MIT have opened a new form of light.