Physics
Double-Slit Experiment with Electrons
The double-slit experiment with electrons is a fundamental demonstration of the wave-particle duality of quantum mechanics. In this experiment, electrons are fired at a barrier with two slits, resulting in an interference pattern on the detection screen, indicating their wave-like behavior. This experiment provides evidence that particles such as electrons can exhibit both wave-like and particle-like properties.
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10 Key excerpts on "Double-Slit Experiment with Electrons"
eBook - PDF- Akira Tonomura(Author)
- 1998(Publication Date)
- World Scientific(Publisher)
Chapter 6 WAVE-PARTICLE DUALITY Up to here, when talking about electron interference phenomena, I have been taking it as a matter of course that electrons are waves. Since we have seen several kinds of interference patterns, you may have been convinced that electrons are waves like the water waves seen in Chapter 2. It also remains true, however, that electrons are particles. An electron is always a particle when detected and has never been divided into two or more pieces. You may think it is paradoxical that electrons have both wave nature and particle nature, but it is the most fundamental principle of quantum mechanics, the law of the microscopic world. Waves or Particles? The particle nature means that an electron is localized at a point, and the wave nature means that an electron is extended in a space. How can electrons have these apparently contradictory properties? The two-slit experiment demonstrating the essence of this problem is almost always introduced at the beginning of quantum mechanics textbooks. I would like to discuss this most important experiment in quantum mechanics here, though many of you may already know about it. The two-slit experiment is an interference experiment in which electrons or pho-tons are incident one by one onto two slits (Fig. 39). The time interval between them is so sparse that at most one electron or photon exists in the apparatus. The experiment using photons, in place of electrons, is described in S. Tomonaga's essay Trial of a Photon. In this essay, a prosecutor asserts that Miss Photon must have passed through one of the two slits since she has never been found split into two or more pieces. Note that a photon in Chinese characters can also be pronounced as Mitsuko, a girl's name. While she insists that the prosecutor is not right, her be-havior is inspected at the scene of the event. We send out photons one by one onto the two slits. The arrival of individual photons is recorded on the screen behind the two slits.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
This showed the effect of measurements that disturbed the particles in transit to a lesser degree and thereby influenced the interference pattern only to a comparable extent. The double slit experiment can also be performed (using a different apparatus) with particles of matter such as electrons with the same results, demonstrating that they also show particle-wave duality. ________________________ WORLD TECHNOLOGIES ________________________ Overview Single-slit diffraction pattern Double-slit diffraction and interference pattern ________________________ WORLD TECHNOLOGIES ________________________ Normally, when only one slit is open, the pattern on the screen is a diffraction pattern, a fairly narrow central band with dimmer bands parallel to it on each side. (See the top photograph) When both slits are open, the pattern displayed becomes very much more detailed and at least four times as wide. (See the bottom photograph) These observations were described by Thomas Young in a paper entitled Experiments and Calculations Relative to Physical Optics, published in 1803. Young placed a single piece of wire between a light source and a screen, and on the screen he observed the fringe pattern. Young explained this pattern using the wave theory of light. To a very high degree of success, these results were explained by the method of the Huygens–Fresnel principle that based its calculations on the hypothesis that light consists of waves propagated through some medium. However, discovery of the photoelectric effect made it necessary to go beyond classical physics and take the quantum nature of light and/or matter into account. It is a widespread misunderstanding that, when two slits are open but a detector is added to the experiment to determine which slit a photon has passed through, then the interference pattern no longer forms and the experimental apparatus yields two simple patterns, one from each slit, superposed without interference.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
The differences in the cumulative action along the different paths produces the interference pattern observed by the double-slit experiment. Feynman stressed that his formulation is merely a mathe-matical description, not an attempt to describe a real process that we cannot measure. Relational interpretation According to the relational interpretation of quantum mechanics, first proposed by Carlo Rovelli, observations such as those in the double-slit experiment result specifically from the interaction between the observer and the object being observed, not any absolute property possessed by the object. In the case of an electron, if it is initially observed at a particular slit, then the observer/particle interaction includes information about the electron's position. This partially constrains the particle's eventual location at the screen. If it is observed not at a particular slit but rather at the screen, then there is no which slit information as part of the interaction, so the electron's observed position on the screen is determined strictly by its probability function. This makes the resulting pattern on the screen the same as if each individual electron had passed through both slits. It has also been suggested that space and distance themselves are relational, and that an electron can appear to be in two places at once — e.g., at both slits — because its spatial relations to particular points on the screen remain identical from both slit locations. ________________________ WORLD TECHNOLOGIES ________________________ When observed emission by emission Electron buildup over time For any particle small enough for quantum effects to be significant—electron, proton, etc.—, where it will arrive at the screen is highly determinate (in that quantum mechanics predicts accurately the probability that it will arrive at any point on the screen).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 9 Double-Slit Experiment Same double-slit assembly (0.7mm between slits); in top image, one slit is closed. Note that the single-slit diffraction pattern — the faint spots on either side of the main band — is also seen in the double-slit image, but at twice the intensity and with the addition of many smaller interference fringes. The double-slit experiment or Thomas Young's experiment involves particle beams or coherent waves passing through two closely-spaced slits, after which in many circumstances they are found to interfere with each other. ________________________ WORLD TECHNOLOGIES ________________________ In quantum mechanics the double-slit experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles (wave–particle duality). The setup used by Young, and by Newton, differs from the modern version; they passed a beam of light over a thin object such as a slip of card (in Young's case) or a hair (in Newton's case). More recently a point light source illuminates a thin plate with two parallel slits, and the light passing through the slits strikes a screen behind them. The beams emerging from the two slits are coherent, in phase, as they are derived from the same source. The wave nature of light causes the coherent light waves passing through the two slits to interfere, creating a pattern of bright and dark bands on the screen. (However, at the screen the light is always found to be absorbed as though it were composed of discrete particles, photons.) Classical particles do not interfere with each other (they can collide, but that is quite different). If classical particles are fired in a straight line through one of a pair of slits they will all strike the screen in a pattern the same size and shape as the slit; if fired through the other slit the result will be similar.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 18 Double-Slit Experiment Same double-slit assembly (0.7mm between slits); in top image, one slit is closed. Note that the single-slit diffraction pattern — the faint spots on either side of the main band — is also seen in the double-slit image, but at twice the intensity and with the addition of many smaller interference fringes. The double-slit experiment or Thomas Young's experiment involves particle beams or coherent waves passing through two closely-spaced slits, after which in many circumstances they are found to interfere with each other. In quantum mechanics the double-slit experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles (wave–particle duality). ________________________ WORLD TECHNOLOGIES ________________________ The setup used by Young, and by Newton, differs from the modern version; they passed a beam of light over a thin object such as a slip of card (in Young's case) or a hair (in Newton's case). More recently a point light source illuminates a thin plate with two parallel slits, and the light passing through the slits strikes a screen behind them. The beams emerging from the two slits are coherent, in phase, as they are derived from the same source. The wave nature of light causes the coherent light waves passing through the two slits to interfere, creating a pattern of bright and dark bands on the screen. (However, at the screen the light is always found to be absorbed as though it were composed of discrete particles, photons.) Classical particles do not interfere with each other (they can collide, but that is quite different). If classical particles are fired in a straight line through one of a pair of slits they will all strike the screen in a pattern the same size and shape as the slit; if fired through the other slit the result will be similar.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 10 Double-slit Experiment Same double-slit assembly (0.7mm between slits); in top image, one slit is closed. Note that the single-slit diffraction pattern — the faint spots on either side of the main band — is also seen in the double-slit image, but at twice the intensity and with the addition of many smaller interference fringes. The double-slit experiment or Young's experiment involves particle beams or coherent waves passing through two closely-spaced slits, after which in many circumstances they are found to interfere with each other. ________________________ WORLD TECHNOLOGIES ________________________ In quantum mechanics the double-slit experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles (wave–particle duality). The setup used by Young, and by Newton, differs from the modern version; they passed a beam of light over a thin object such as a slip of card (in Young's case) or a hair (in Newton's case). More recently a point light source illuminates a thin plate with two parallel slits, and the light passing through the slits strikes a screen behind them. The beams emerging from the two slits are coherent, in phase, as they are derived from the same source. The wave nature of light causes the coherent light waves passing through the two slits to interfere, creating a pattern of bright and dark bands on the screen. (However, at the screen the light is always found to be absorbed as though it were composed of discrete particles, photons.) Classical particles do not interfere with each other (they can collide, but that is quite different). If classical particles are fired in a straight line through one of a pair of slits they will all strike the screen in a pattern the same size and shape as the slit; if fired through the other slit the result will be similar.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 5 Double-Slit Experiment Same double-slit assembly (0.7mm between slits); in top image, one slit is closed. Note that the single-slit diffraction pattern — the faint spots on either side of the main band — is also seen in the double-slit image, but at twice the intensity and with the addition of many smaller interference fringes. The double-slit experiment or Young's experiment involves particle beams or coherent waves passing through two closely-spaced slits, after which in many circumstances they are found to interfere with each other. In quantum mechanics the double-slit experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles (wave–particle duality). The setup used by Young, and by Newton, differs from the modern version; they passed a beam of light over a thin object such as a slip of card (in Young's case) or a hair (in ________________________ WORLD TECHNOLOGIES ________________________ Newton's case). More recently a point light source illuminates a thin plate with two parallel slits, and the light passing through the slits strikes a screen behind them. The beams emerging from the two slits are coherent, in phase, as they are derived from the same source. The wave nature of light causes the coherent light waves passing through the two slits to interfere, creating a pattern of bright and dark bands on the screen. (However, at the screen the light is always found to be absorbed as though it were composed of discrete particles, photons.) Classical particles do not interfere with each other (they can collide, but that is quite different). If classical particles are fired in a straight line through one of a pair of slits they will all strike the screen in a pattern the same size and shape as the slit; if fired through the other slit the result will be similar.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 9 Double-Slit Experiment Same double-slit assembly (0.7mm between slits); in top image, one slit is closed. Note that the single-slit diffraction pattern — the faint spots on either side of the main band — is also seen in the double-slit image, but at twice the intensity and with the addition of many smaller interference fringes. The double-slit experiment or Young's experiment involves particle beams or coherent waves passing through two closely-spaced slits, after which in many circumstances they are found to interfere with each other. In quantum mechanics the double-slit experiment demonstrates the inseparability of the wave and particle natures of light and other quantum particles (wave–particle duality). The setup used by Young, and by Newton, differs from the modern version; they passed a beam of light over a thin object such as a slip of card (in Young's case) or a hair (in ________________________ WORLD TECHNOLOGIES ________________________ Newton's case). More recently a point light source illuminates a thin plate with two parallel slits, and the light passing through the slits strikes a screen behind them. The beams emerging from the two slits are coherent, in phase, as they are derived from the same source. The wave nature of light causes the coherent light waves passing through the two slits to interfere, creating a pattern of bright and dark bands on the screen. (However, at the screen the light is always found to be absorbed as though it were composed of discrete particles, photons.) Classical particles do not interfere with each other (they can collide, but that is quite different). If classical particles are fired in a straight line through one of a pair of slits they will all strike the screen in a pattern the same size and shape as the slit; if fired through the other slit the result will be similar.
eBook - ePubQuantum Mechanics I
The Fundamentals
- S. Rajasekar, R. Velusamy(Authors)
- 2022(Publication Date)
- CRC Press(Publisher)
34 ]. Later the double slit interference pattern was also observed even if one particle at a time passed through the double slit apparatus. Experiment with double slit has has also proved that any experiment in which the path of the particle is measured will not show any interference pattern. A slit detector can find whether a particle passed through it or not.Wheeler raised a question whether we can observe the interference pattern by detecting the path of the particle through the slit after the particle has passed through the slit. The question is whether the particle decides to behave as a particle or wave at the slits itself irrespective of its path determined later. Wheeler's thought experiment has been tested using Mach–Zehnder interferometer using a second beam splitter. The absence of the second beam splitter will reveal the particle nature and the presence of it will show interference pattern corresponding to wave nature of the particle. The removal and inclusion of the second beam splitter can be delayed even after the particle has passed through the first beam splitter. This experiment established that particle behaves as wave or particle depending on the final detection arrangements only.The above mentioned experiments were done using a quantum beam splitter using Hadamard quantum gate with the control of an ancilla photon. This ancilla photon can be in a superposition state of present and absent and it is possible to prepare a photon state in a superposition of particle and wave. It is also possible to create a pair of entangled photons, a signal photon and an ancillary photon. The ancillary photon carries which-way information of the signal photon. It is possible to erase this information on the ancillary photon after the signal photon has been detected. Such an erasure of the which-way information correlated with the signal information will give interference pattern. The time order of the measurement of signal photon and ancillary photon is of no consequence.
eBook - PDFQuantized Detector Networks
The Theory of Observation
- George Jaroszkiewicz(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
10 Double-Slit Experiments 10.1 Introduction In this chapter we show how the quantized detector network (QDN) formal- ism describes the double-slit (DS) experiment. This is arguably the simplest experiment that demonstrates quantum affects such as wave–particle duality and quantum interference. It continues to be the focus of much debate and experiment (Mardari, 2005), because theoretical modeling of what is going on reflects current understanding of quantum physics and hence physical reality. We will apply QDN to two variants: the original DS experiment and the monitored DS experiment, where an attempt is made to determine the imagined path of the particle. The DS experiment is widely acknowledged by physicists to be of importance to the understanding of quantum mechanics (QM). So much so that in 2002, the single electron version, first performed by Merli, Missiroli, and Pozzi (Merli et al., 1976), was voted by readers of Physics World to be “the most beautiful experiment in physics” (Rosa, 2012). The DS experiment can be discussed in terms of three stages, shown in Figure 10.1. By the end of the preparation stage, Σ 0 , a monochromatic beam of light or particles has been prepared by a source P , such as a laser. The beam emerges from point O and then passes through an information void V 1 to the first stage, Σ 1 , which consists of a wall or barrier W . This wall has two openings denoted A and B that allow parts of the beam to pass through into another information void V 2 and onto the second and final stage Σ 2 , which consists of a detecting screen S. The screen S is in general some material that can absorb and record particle impacts. In reality, any screen will consist of a finite number of signal detectors, such as photosensitive molecules, but the typical QM modeling is done as if there were a continuum of sites on the screen, such as C , that could register particles. 132 Double-Slit Experiments P O A E W B S C D V V z Figure 10.1.
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