A magneto optical trap (MOT) is the primary method by which dilute gasses of atoms and molecules are taken from room temperature to the sub-Kelvin range. It is the first step in many experiments and technologies related to high-accuracy atomic clocks, cold atom gyroscopes and accelerometers used in inertial navigation devices, magnetic field sensors, quantum computing, and gravimeters used to detect underground tunnels, aquifers, or other underground natural resources.
A MOT uses laser beams and magnetic fields to collect a high density of atoms with low kinetic energy. For example, a three-dimensional MOT can collect a small cloud, approximately 4 mm across, of super-cooled atoms where the average speed of an atom in the MOT is on the order of 0.1 meters per second. This is compared to atoms at room temperature moving at hundreds of meters per second.
Prior methods of creating three-dimensional MOTs used six counter-propagating light beams pointed along the cardinal axes towards a common intersection to capture cold atoms. See, for example, Matthieu Vangeleyn's PhD thesis at the University of Strathclyde, entitled “Atom trapping in non-trivial geometries for micro-fabrication applications.” Another method replaces two of the six beams with mirrors. Still another method uses a single laser with a corner-cube reflector or reflecting right cone to capture atoms within the reflector.