Condensate is a group of atoms cooled to within a hair of absolute zero. When they reach that temperature, the atoms are hardly moving relative to each other. They have almost no free energy to do so. At that point, the particles begin to clump together and enter the same energy states. They become identical, from a physical point of view, and the whole group starts behaving as though it were a single atom.
It is also known as Bose-Einstein condensate, and you start the experiment with a cloud of gas. Many experiments start with atoms of rubidium. Then you cool it with lasers, using the beams to take energy away from the atoms. After that, to cool them further, scientists use evaporative cooling.
“With a Bose-Einstein condensate, you start from a disordered state, where kinetic energy is greater than potential energy. You cool it down, but it doesn’t form a lattice-like a solid,” said Xuedong Hu (professor of physics at the University at Buffalo).
Scientists found ghost particles in condensate of light and matter
Physicists at the Australian National University, use exciton-polaritons, hybrid particles with both light and matter character, which allows detection of momentum without any distortion.
Instead, the atoms fall into the same quantum states, and can’t be distinguished from one another. At that point, the atoms start obeying what is called Bose-Einstein statistics, which are usually applied to particles you can’t tell apart, such as photons.
A surprising result of the study offers a new challenge for physics. The exciting thing about these particles is that even though they are strictly not part of the condensate, they tell you everything about the condensate. All these formulas and substance combination makes us see a ghostly part of this phenomenon. Maybe when we see a ghost, it’s a Bose-Einstein reaction, and our mind is playing tricks on us.