text: Samples of ultracold atoms are typically prepared through the interactions of a dilute gas with a laser field. Evidence for radiation pressure, force due to light on atoms, was demonstrated independently by Lebedev, and Nichols and Hull in 1901. In 1933, Otto Frisch demonstrated the deflection of individual sodium particles by light generated from a sodium lamp.
  The invention of the laser spurred the development of additional techniques to manipulate atoms with light. Using laser light to cool atoms was first proposed in 1975 by taking advantage of the Doppler effect to make the radiation force on an atom dependent on its velocity, a technique known as Doppler cooling. Similar ideas were also proposed to cool samples of trapped ions. Applying Doppler cooling in three dimensions will slow atoms to velocities that are typically a few cm/s and produce what is known as an optical molasses.
  Typically, the source of neutral atoms for these experiments were thermal ovens which produced atoms at temperatures of a few hundred kelvins. The atoms from these oven sources are moving at hundred of meters per second.  One of the major technical challenges in Doppler cooling was increasing the amount of time an atom can interact with the laser light. This challenge was overcome by the introduction of a Zeeman Slower. A Zeeman Slower uses a spatially varying magnetic field to maintain the relative energy spacing of the atomic transitions involved in Doppler cooling. This increases the amount of time the atom spends interacting with the laser light. Experiments can also use metal dispensers, which are pure metal (typically alkali metals) rods that can emit when heated up  (the vapor pressure is higher) with electrical current.
  The development of the first magneto-optical trap (MOT) by Raab et al. in 1987 was an important step towards the creation of samples of ultracold atoms. Typical temperatures achieved with a MOT are tens to hundreds of microkelvins. In essence, a magneto optical trap confines atoms in space by applying a magnetic field so that lasers not only provide a velocity dependent force but also a spatially varying force. The 1997 Nobel prize in physics was awarded for development of methods to cool and trap atoms with laser light and was shared by Steven Chu, Claude Cohen-Tannoudji and William D. Phillips.
  Evaporative cooling was used in experimental efforts to reach lower temperatures in an effort to discover a new state of matter predicted by Satyendra Nath Bose and Albert Einstein known as a Bose–Einstein condensate (BEC). In evaporative cooling, the hottest atoms in a sample are allowed to escape  which reduces the average temperature of the sample. The Nobel Prize in 2001 was awarded to  Eric A. Cornell, Wolfgang Ketterle and Carl E. Wieman for the achievement of Bose–Einstein condensate in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates.
  In recent years a variety of sub-Doppler cooling techniques, including polarization gradient cooling, gray molasses cooling, and Raman sideband cooling, have enabled the cooling and trapping of single atoms in optical tweezers. Experimental platforms leveraging ultracold neutral atoms in optical tweezers and optical lattices have become an increasingly popular setting for studying quantum computing, quantum simulation, and precision metrology. Atoms with closed cycling transitions, capable of scattering many photons with a low probability of decay into other states, are common choices of species for ultracold neutral atom experiments. The lowest-energy fine structure transitions in alkali atoms enable fluorescence imaging, while a combination of hyperfine and Zeeman sublevels can be used for implementing sub-Doppler cooling. Alkaline earth atoms have also gained  popularity owing to narrow-linewidth cooling transitions and ultra-narrow optical clock transitions.