What is Bose Einstein Condensate?

Bose Einstein condensate emerged in 1995 as an example of an incredibly cold fifth state of matter, a superfluid. Our universe is composed of gas, liquid, solid, and plasma, but physics predicts another form of matter that does not exist naturally. The particles in Bose Einstein condensate have the coldest temperature possible, 0 degrees Kelvin, or absolute zero. Consequently, particles in this state display unique, even bizarre, characteristics.

In 1924, the physicists Satyendra Nath Bose and Albert Einstein theorized that this other state of matter must be possible. Einstein expounded on Bose's ideas about the behavior of light when acting as waves and particles. He applied the strange statistics which described how light can coalesce into a single entity (now known as a laser) and wondered how it might impact particles with mass. But they were many years from having sophisticated enough instruments to test the theory of particles condensing into a new state.

When Carl Wieman and Eric Cornell cooled rubidium-87 to within billionths of a degree of absolute zero, Bose Einstein condensate (BEC) was born. They had to be careful and creative to cool these special particles, known as bosons, using a combination of lasers and magnets. For their efforts, they were rewarded the Nobel Prize in 2001. We can't yet cool particles such that their movement due to heat stops entirely (true absolute zero), but getting them to less than one millionth of a degree Kelvin suffices to show the properties of Bose Einstein condensate.

What sets bosons apart from other particles is their integer "spin," as opposed to regular particles. The separate electrons in composite bosons tend to occupy the exact same energy level at the same time, which means that the atoms have coalesced into the same exact entity. We can look at this single unit and see one fuzzy point, instead of several separate atoms. Other bosons, like helium-4, can also be forced into a BEC.

When bosons collapse their identities into a single identity, they visually show us the wave-particle duality in a new way. BEC, with its similarity to lasers, could revolutionize certain technologies. Their characteristic superfluidity means they flow without losing any energy to friction, so they are an efficient source of energy. In the future, they might be used to etch on the nano-level or accelerate matter close to the speed of light.