Bose-Einstein condensate: a standalone construct

Satyendra Nath Bose's 1924 paper Plancks Gesetz und Lichtquantenhypothese derived Planck's radiation law by treating light quanta as indistinguishable particles, and Albert Einstein, extending Bose's counting method to the atoms of an ideal gas in 1924 and 1925, predicted that below a critical temperature a large fraction of those atoms would drop into the single lowest-energy quantum state, forming a new state of matter. The particles that can do this are bosons, meaning particles that are allowed to share the same quantum state without limit, and in a Bose-Einstein condensate a macroscopic number of them occupy that one ground state at once, so the whole cloud behaves as a single quantum object rather than a crowd of independent atoms. The prediction was realized experimentally in 1995, first by Eric Cornell, Carl Wieman, and colleagues at JILA using rubidium atoms cooled to about 170 nanokelvin (Anderson et al., 1995), and shortly afterward by Wolfgang Ketterle's group at MIT using sodium (Davis et al., 1995), work recognized with the 2001 Nobel Prize in Physics. What makes the condensate a landmark is that it renders quantum coherence visible at laboratory scale: a shared wavefunction and matter-wave interference, normally confined to single particles, appear across an entire population of atoms, and the state underpins later study of superfluidity, atom interferometry, and matter-wave optics.[1][2][3][4]

Unit

A thermodynamic phase of a dilute boson gas, defined by macroscopic occupation of the single-particle ground state below a critical temperature

Recovery means

Not applicable

Measured by

Identified by cooling a trapped boson gas below its critical temperature and observing the emergence of a sharp, bimodal peak in the atoms' velocity or density distribution, typically through time-of-flight absorption imaging