What is a Bose-Einstein condensate?Asked by: Umair Kayani
AnswerBose-Einstein condensation is a phenomenon that occurs at low temperatures in systems consisting of large numbers of bosons whose total number is conserved in collisions. Used in the explanation of superfluidity, this phenomenon enables a significant fraction of the particles to occupy a single quantum state. No analogous phenomenon occurs for two or more fermions, which are prohibited by the Pauli exclusion principle from occupying the same quantum state.
This property of making a group of bosons into the same quantum state so they act like a single entity was done in 1995 by physicists at the Joint Institute of Laboratory Astrophysics, in Boulder, Colorado. They succeed in cooling about 2000 atoms of rubidium gas to 170 nanokelvin (170 billionths of a degree above absolute Kelvin), where they formed a Bose-Einstein condensate less than 100 micrometers across. The condensate lasted for about 15 seconds, and was cooled all the way down to 20 nanokelvin. If the technique can be extended to large aggregates, it will make single 'quantum particles' visible.
Answered by: Dan Summons, Physics Undergrad Student, UOS, Souhampton