Physicists have shown that only 7 quantum particles are needed, that they behaved as if they were immersed in a billion crowd. On a large scale, matter passes through various transformations, referred to as phase transitions, where (for example) water passes into ice or steam. Researchers are used to seeing things like this in large masses of molecules, but never in such a tiny cluster.
In a new study, scientists tracked phase transitions in systems represented by seven light particles (photons) that acquired an exotic physical state — the Bose-Einstein condensate (BCE). It is a physical state that is reached by matter at ultracold temperatures, where particles begin to mix and act in unison.
Since photons are packets of light, they are created from energy, not matter, which makes it strange to change the phase. But back in 2010, German researchers were able to show that light particles capable of behaving like CBA. To catch the photons, scientists created a small mirror camera and filled it with colored paint. When light particles crashed into the dye particles, the latter absorbed the first and re-emitted. Because of this, the photons took more time to move around the camera, which actually slowed them down. As a result, the camera became a space where researchers could make photons sluggish and put them in close distances. As a result, it was evident how the photons begin to contact and demonstrate CBE. In a recent experiment, the team wanted to find out the minimum number of photons required for such actions. Using a fine laser, they pumped photons into a similarly filled dye mirror trap one by one and observed the behavior of the mixture. It turned out that, on average, 7 photons are enough to form a CBE. This low threshold is necessary to determine the start of a phase transition.
Scientists have noted some differences in micro-CBA from phase transitions with a larger number of particles. When the ice heats up more than the melting point, it seems that it goes from solid to liquid form instantly. However, with the participation of only 7 photons, this process is carried out gradually.
