A Bose-Einstein condensate was produced in a vapor of rubidium-87 atoms that was confined by magnetic fields and evaporatively cooled. The condensate fraction first appeared near a temperature of 170 nanokelvin and a number density of 2.5 x 10 12 per cubic centimeter and could be preserved for more than 15 seconds. Three primary signatures of Bose-Einstein condensation were seen. (i) On top of a broad thermal velocity distribution, a narrow peak appeared that was centered at zero velocity. (ii) The fraction of the atoms that were in this low-velocity peak increased abruptly as the sample temperature was lowered. (iii) The peak exhibited a nonthermal, anisotropic velocity distribution expected of the minimum-energy quantum state of the magnetic trap in contrast to the isotropic, thermal velocity distribution observed in the broad uncondensed fraction.

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Observation of Bose-Einstein Condensation in a Dilute Atomic Vapor

The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary role in areas of the physical and biological sciences. This paper reviews the early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology. Some further major achievements of these rapidly developing methods also are considered.

/pdf/optical-trapping-and-manipulation-of-neutral-particles-using-4qf0uymz6l.pdf

Optical trapping and manipulation of neutral particles using lasers

https://link.aps.org/pdf/10.1103/RevModPhys.70.721

Nobel Lecture: Laser cooling and trapping of neutral atoms

The basic physical effects leading to radiation-induced forces are reviewed. A simple derivation of the mathematical expressions for the classical light forces is given. The influence of quantum fluctuations is demonstrated and the possibilities for trapping neutral particles are discussed. Two recent successful laser cooling and trapping experiments are described to illustrate the applications of the basic principles.

https://iopscience.iop.org/article/10.1088/0143-0807/9/4/001/pdf

Laser cooling and trapping

Publisher Summary This chapter discusses optical dipole traps for neutral atoms Methods for storage and trapping of charged and neutral particles have very often served as the experimental key to great scientific advances, covering physics in the vast energy range from elementary particles to ultracold atomic quantum matter It describes the basic physics of dipole trapping in fardetuned light, the typical experimental techniques and procedures, and the different trap types currently available, along with their specific features In the experiments discussed, optical dipole traps have already shown great promise for a variety of different applications Of particular importance is the trapping of atoms in the absolute internal ground state, which cannot be trapped magnetically In this state, inelastic binary collisions are completely suppressed for energetic reasons In this respect, an ultracold cesium gas represents a particularly interesting situation, because Bose–Einstein condensation seems attainable only for the absolute ground state Therefore, an optical trap may be the only way to realize a quantum-degenerate gas of Cs atoms Further, optical dipole traps can be seen as storage devices at the low end of the presently explorable energy scale Future experiments exploiting the particular advantages of these traps can reveal interesting new phenomena

Optical Dipole Traps for Neutral Atoms

We report the confinement and cooling of an optically dense cloud of neutral sodium atoms by radiation pressure. The trapping and damping forces were provided by three retroreflected laser beams propagating along orthogonal axes, with a weak magnetic field used to distinguish between the beams. We have trapped as many as ${10}^{7}$ atoms for 2 min at densities exceeding ${10}^{11}$ atoms ${\mathrm{cm}}^{\ensuremath{-}3}$. The trap was \ensuremath{\simeq}0.4 K deep and the atoms, once trapped, were cooled to less than a millikelvin and compacted into a region less than 0.5 mm in diameter.

Trapping of neutral sodium atoms with radiation pressure

Light traps using spontaneous forces (A)

We show that the optical Earnshaw theorem does not always apply to atoms and that it is possible to confine atoms using spontaneous light forces produced by static laser beams. A necessary condition for such traps is that the atomic transition rate is not a function of the light intensity only. We give general approaches which satisfy this condition and present a new trap design utilizing these principles. This trap has a depth on the order of a kelvin and a volume of several cm3.

E. L. Raab

Papers

Trapping of neutral sodium atoms with radiation pressure

Light traps using spontaneous forces (A)

Trapping atoms with radiation pressure