The Magic of Matter Waves
Short summary:
atoms are reected, diffracted and interfere using various atom-optical elements. mit physics annual 2001. figure 2. Observation of atom amplication. ...
Long summary:
The Magic of Matter Waves he hypothesis of Louis de Broglie in 1924 that all material particles have wave properties is one of the basic tenets of quantum physics. The duality that particles propagate as waves, but are detected as particles, is one of the counterintuitive aspects of physics that every student has to digest. However, the wavelength of the de Broglie waves is so small that the wave character of matter only becomes manifest in the microscopic domain. For example, the matter wavelength of room temperature atoms is smaller than the atom itself. The wavelength of a macroscopic body is more than a billion times smaller. This is the reason we dont experience the wave properties of matter in everyday life. This situation dramatically changes at extremely low temperatures when the motion of particles slows down and their de Broglie wavelength db , which is inversely 44 ) ketterle mit physics annual 2001 Wolfgang Ketterle The Magic of Matter Waves proportional to their velocity v, increases: db = h/mv. Here h is Plancks constant and m the atomic mass. Recent advances in atom cooling makes it now possible to reach nanokelvin temperatures. The matter wavelength of atoms, which is of subatomic scale at room temperature, becomes macroscopic at such low temperatures and determines the properties of a gaseous sample, the size of which is comparable to the thickness of a hair. Atomic matter waves can now be directly photographed, and ultracold matter with novel properties can be studied. The wavelike properties of atoms become very dramatic through the phenomenon of Bose-Einstein condensation (BEC). When the temperature is sufficiently low and the de Broglie wavelength of the atoms becomes comparable to the distance between atoms, then almost all the atoms occupy a single quantum state. They become one giant matter wave all oscillating in phase. This new form of matter is called a Bose-Einstein condensate. The 1997 issue of physics@mit included a description of this phenomenon and of the experimental verication of the coherence of the condensate done in Prof. Ketterles group. That article also described the cooling and trapping techniques necessary to produce condensates. Manyof these techniques were pioneered by groups at MIT led by Professors Pritchard, Greytak and Kleppner. After the feat of cooling an initially hot gas down to nanokelvin temperatures is accomplished, one obtains a cloud of about ten million sodium atoms in a volume of a fraction of a millimeter, at a density one hundred thousand times less than air. This cloud is magnetically suspended and conned in an ultrahigh vacuum chamber. The study of its properties is currently one of the hottest areas in physics and the topic of about 500 scientic publications every year. Research on gaseous BEC can be divided into two areas: In the rst (which could be labeled The atomic condensate as a coherent gas, or Atom lasers), one would like to have as little interaction as possible almost ...
Source: web.mit.edu
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