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A system composed of a handful of particles acts as larger systems, which allows scientists to more easily study quantum behavior.
Most of the substances that physicists study are composed of a large number of particles – so large that there is practically no difference between the behavioral properties of a drop of pure water and those of a swimming pool. Even a single drop can contain more than one quadrillion particles.
This facilitates understanding of their collective behavior. For example, the water in the drop of water and in the pool will freeze at 0 degrees Celsius and boil at 100 degrees Celsius.
Such "phase transitions" (that is, from liquid to solid or from liquid to gas) can appear suddenly in these large systems, because there are so many particles involved that they all seem to act in same time. But what about in much smaller systems? When there is only a handful of particles, do the same phase transition rules apply?
To answer these questions, a team of scientists from Imperial College London, Oxford University and the Institute of Technology Karlsruhe, Germany, fabricated a system of less than 10 photons, the fundamental particles light. The results of their experiments, published today in Physics of nature, show that phase transitions still occur in systems consisting of only seven particles on average.
The study of the quantum behavior of particles is much easier with fewer particles, so the fact that phase transitions occur in these small systems allows scientists to more easily study quantum properties such as coherence.
Lead author, Dr. Robert Nyman, of the Department of Physics of Imperial, said: "Now that it is confirmed that the" phase transition "is still a useful concept in these little ones. systems, we can explore properties that would not be possible in larger systems. .
"In particular, we can study the quantum properties of matter and light – which happens at the smallest scale when phase transitions occur."
The system that the team studied was a Bose-Einstein condensate (BEC) of photons. BECs are formed when a quantum particle gas is so cold or so close that it can no longer be distinguished. A BEC is a state of matter that has properties very different from those of solids, liquids, gases or plasmas.
The team found that by adding photons to the system, a phase transition to a BEC would occur once the system reaches about seven photons, less than in any other BEC seen before. So small, the transition was less abrupt than in large systems such as watersheds, but the fact that the transition took place to a predictable point reflects the larger systems.
The system was created with a simple device – some fluorescent dyes and curved mirrors. This means that in addition to being useful in the study of quantum properties, the system could be used to create and manipulate special states of light.
The co-author, Dr. Florian Mintert, of the Department of Physics of Imperial, said: "With the best of two distinct worlds – the physics of phase transitions and the accessibility of small systems – this source unusual light has potential applications in measurement or detection. "
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Material provided by Imperial College London. Note: Content can be changed for style and length.
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