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The modern double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles; moreover, it displays the fundamentally probabilistic nature of quantum mechanical phenomena. A simpler form of the double-slit experiment was performed originally by Thomas Young in 1801 (well before quantum mechanics). He believed it demonstrated that the wave theory of light was correct and his experiment is sometimes referred to as Young's experiment〔. While there is no doubt that Young's demonstration of optical interference, using sunlight, pinholes and cards, played a vital part in the acceptance of the wave theory of light, there is some question as to whether he ever actually performed a double-slit interference experiment. *〕 or ''Young's slits''. The experiment belongs to a general class of "double path" experiments, in which a wave is split into two separate waves that later combine into a single wave. Changes in the path lengths of both waves result in a phase shift, creating an interference pattern. Another version is the Mach–Zehnder interferometer, which splits the beam with a mirror.In the basic version of this experiment, a coherent light source such as a laser beam illuminates a plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. The wave nature of light causes the light waves passing through the two slits to interfere, producing bright and dark bands on the screen—a result that would not be expected if light consisted of classical particles.〔〔Feynman, 1965, p. 1.5〕 However, the light is always found to be absorbed at the screen at discrete points, as individual particles (not waves), the interference pattern appearing via the varying density of these particle hits on the screen. Furthermore, versions of the experiment that include detectors at the slits find that each detected photon passes through one slit (as would a classical particle), and not through both slits (as would a wave).〔Feynman, 1965, p. 1.7〕〔(Lederman, 2011, p. 109 )〕〔"''...if in a double-slit experiment, the detectors which register outcoming photons are placed immediately behind the diaphragm with two slits: A photon is registered in one detector, not in both...''" 〕〔"''It seems that light passes through one slit or the other in the form of photons if we set up an experiment to detect which slit the photon passes, but passes through both slits in the form of a wave if we perform an interference experiment.''" 〕 These results demonstrate the principle of wave–particle duality.〔Feynman, ''Lectures on Physics'' 3:Quantum Mechanics p.1-1 "There is one lucky break, however— electrons behave just like light.".〕〔See: Davisson–Germer experiment 〕 Other atomic-scale entities such as electrons are found to exhibit the same behavior when fired towards a double slit.〔 Additionally, the detection of individual discrete impacts is observed to be inherently probabilistic, which is inexplicable using classical mechanics.〔 The experiment can be done with entities much larger than electrons and photons, although it becomes more difficult as size increases. The largest entities for which the double-slit experiment has been performed were molecules that each comprised 810 atoms (whose total mass was over 10,000 atomic mass units).〔"(Physicists Smash Record For Wave-Particle Duality )"〕 ==Overview== If light consisted strictly of ordinary or classical particles, and these particles were fired in a straight line through a slit and allowed to strike a screen on the other side, we would expect to see a pattern corresponding to the size and shape of the slit. However, when this "single-slit experiment" is actually performed, the pattern on the screen is a diffraction pattern in which the light is spread out. The smaller the slit, the greater the angle of spread. The top portion of the image on the right shows the central portion of the pattern formed when a red laser illuminates a slit and, if one looks carefully, two faint side bands. More bands can be seen with a more highly refined apparatus. Diffraction explains the pattern as being the result of the interference of light waves from the slit. If one illuminates two parallel slits with a more intense red laser, the light from the two slits again interferes. Here the interference is a more pronounced pattern with a series of light and dark bands. The width of the bands is a property of the frequency of the illuminating light.〔Charles Sanders Peirce first proposed the use of this effect as an artifact-independent reference standard for length *C.S. Peirce (July 1879) "Note on the Progress of Experiments for Comparing a Wave-length with a Metre" ''American Journal of Science'', as referenced by Crease, Robert P. (2011). ''World in the Balance: the historic quest for an absolute system of measurement''. New York: W.W. Norton. p. 317. ISBN 978-0-393-07298-3. p. 203.〕 (See the bottom photograph to the right.) When Thomas Young (1773–1829) first demonstrated this phenomenon, it indicated that light consists of waves, as the distribution of brightness can be explained by the alternately additive and subtractive interference of wavefronts.〔 Young's experiment, performed in the early 1800s, played a vital part in the acceptance of the wave theory of light, vanquishing the corpuscular theory of light proposed by Isaac Newton, which had been the accepted model of light propagation in the 17th and 18th centuries. However, the later discovery of the photoelectric effect demonstrated that under different circumstances, light can behave as if it is composed of discrete particles. These seemingly contradictory discoveries made it necessary to go beyond classical physics and take the quantum nature of light into account. The double-slit experiment (and its variations) has become a classic thought experiment, for its clarity in expressing the central puzzles of quantum mechanics. Because it demonstrates the fundamental limitation of the ability of the observer to predict experimental results, Richard Feynman called it "a phenomenon which is impossible () to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the ''only'' mystery (quantum mechanics )."〔 Feynman was fond of saying that all of quantum mechanics can be gleaned from carefully thinking through the implications of this single experiment. Richard Feynman also proposed (as a thought experiment) that if detectors were placed before each slit, the interference pattern would disappear.〔Feynman, 1965, chapter 3〕 The Englert–Greenberger duality relation provides a detailed treatment of the mathematics of double-slit interference in the context of quantum mechanics. A low-intensity double-slit experiment was first performed by G. I. Taylor in 1909, by reducing the level of incident light until photon emission/absorption events were mostly nonoverlapping. A double-slit experiment was not performed with anything other than light until 1961, when Claus Jönsson of the University of Tübingen performed it with electrons.〔Jönsson C, (1961) ''Zeitschrift für Physik'', 161:454–474 〕 In 1974 the Italian physicists Pier Giorgio Merli, Gian Franco Missiroli, and Giulio Pozzi repeated the experiment using single electrons, showing that each electron interferes with itself as predicted by quantum theory. In 2002, the single-electron version of the experiment was voted "the most beautiful experiment" by readers of ''Physics World.''〔("The most beautiful experiment" ). Physics World 2002.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Double-slit experiment」の詳細全文を読む スポンサード リンク
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