In the early days of quantum physics, in the early 20th century, Indian physicist and mathematician Satyendra Nath Bose reinterpreted statistics on the relationship between light and temperature by applying recent advances in quantum theory.
On checking his thinking with Albert Einstein, Bose’s new interpretation became known as Bose-Einstein statistics, a concept that became fundamental in mathematics that allows us to distinguish certain particles from one another when they are in this super-particle cloud.
Bose-Einstein condensation is a phenomenon in physics that occurs in a gas of bosons (particles with integer spin, such as photons, atoms of helium-4, and composite particles like mesons) at low temperatures.
At high temperatures, bosons behave like other particles, such as fermions, and occupy different energy levels according to their energy distribution. However, as the temperature decreases, the bosons become more likely to occupy the same energy level due to their tendency to cluster together, which is known as the Bose-Einstein statistics.
Sometimes referred to as the 'fifth state of matter', a Bose-Einstein Condensate is a state of matter created when particles, called bosons, are cooled to near absolute zero (-273.15 degrees Celsius, or -460 degrees Fahrenheit). At such low temperatures, there is insufficient energy for the particles to move into positions that might cause their distinct quantum characteristics to interfere with one another. Without differences in energy to set particles apart, the whole group comes to share the same quantum identity, effectively becoming a single 'super-particle' cloud, operating under its own rules.
Therefore, when the temperature drops below a certain critical temperature, the bosons start to condense into the lowest possible energy level, forming a Bose-Einstein condensate (BEC). In this state, all the bosons occupy the same quantum state, and they behave like a single entity, rather than as individual particles.
The formation of a BEC leads to some unusual and interesting phenomena. For example, a BEC can exhibit superfluidity, which means that it can flow without any viscosity or resistance, even in the absence of gravity. BECs can also exhibit interference patterns similar to those observed in waves, as well as quantized vortices and other topological defects.
The first experimental observation of BEC was in 1995 in a gas of rubidium atoms by Eric Cornell and Carl Wieman at JILA, and shortly afterwards by Wolfgang Ketterle at MIT in a gas of sodium atoms. Since then, BECs have been studied in a variety of different systems, including ultracold atoms, molecules, and even photons in a Bose-Einstein condensate of light. BECs are a fascinating area of research in modern physics, and they have applications in fields such as quantum information processing, precision measurement, and quantum simulation.