Bose-Einstein condensate is an extreme physical state that usually occurs only at very low temperatures. The particles in this system are no longer distinguishable and are mainly in the same quantum mechanical state. In other words, they behave like a giant “super particle”. Therefore, the state can be described by a single wave function.
In 2010, researchers led by Martin Weitz succeeded in producing Bose-Einstein condensate from light particles (photons) for the first time. Their special system is still in use today: physicists trap light particles in a resonator composed of two curved mirrors, the distance between the two mirrors is just over one micrometer, and they reflect the fast reciprocating beam. This space is filled with a liquid dye solution, which can be used to cool the photons. The dye molecules “engulf” the photons and then spit them out again, which brings the light particles to the temperature of the dye solution-equivalent to room temperature. The system can cool lightweight particles because their natural characteristic is that they dissolve when cooled.
Clear separation of the two phases
The phase transition is what physicists call the transition between water and ice during freezing. But how does a specific phase change occur within the captured light particle system? Scientists explain it like this: a semi-transparent mirror will cause photons to be lost and replaced, resulting in non-equilibrium, causing the system to be unable to assume a certain temperature and enter an oscillation state. This creates a transition between the oscillating phase and the damping phase. Damping means that the amplitude of vibration is reduced.
Fahri EmreÖztürk, a doctoral student at the Institute of Applied Physics at the University of Bonn, said: “It can be said that the over-damping phase we observe corresponds to the new state of the light field.” The effects of color-Einstein condensate are separated, and there is no clearly defined boundary between the two states. This means that physicists can constantly move back and forth between effects.
“However, in our experiment, the overdamped state of the optical Bose-Einstein condensate was separated by oscillation and the phase change of the standard laser,” said research leader Professor Martin Weitz. He said: “This shows that there is a Bose-Einstein condensate, and its state is actually different from that of the standard laser.” In other words, we are dealing with two optical Bose-Einstein condensates. Independent phase.
The researchers plan to use their findings as the basis for further research to find new states of the light field in a variety of coupled photocondensates, which may also occur in the system. Fahri Emre Öztürk said: “If a suitable quantum mechanical entangled state appears in the coupled light condensate, this may be interesting for transmitting quantum encrypted messages between multiple participants.”
Physicists split irreversibly by freezing photons in Bose-Einstein condensate
“Observing the non-Hemet phase transition in light quantum gas” science (2021). science.sciencemag.org/cgi/doi…1126 / science.abe9869
Provided by the University of Bonn
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