We have seen that a quantum particle like an electron has wave-like features and that an electromagnetic wave has particle-like properties as we may consider such a wave as a collective of photons. This naturally raises the question how quantum particles really exhibit these wave-like properties. In this chapter we focus on the question of whether particles can show interference effects like waves do. The answer to this question is affirmative, as is demonstrated by the famous double slit experiments of various kinds. In this chapter we consider classical as well as quantum wave phenomena.
We have seen that a quantum particle like an electron has wave-like features and that an electromagnetic wave has particle-like properties as we may consider such a wave as a collective of photons. This naturally raises the question how quantum particles really exhibit these wave-like properties. In this chapter we focus on the question of whether particles can show interference effects like waves do. The answer to this question is affirmative, as is demonstrated by the famous double slit experiments of various kinds. In this chapter we consider classical as well as quantum wave phenomena.
Abstract Chapter 11 introduces the essential mystery of quantum mechanics, shows how it is resolved, and then goes on to examine related phenomena. The mystery is how individual photons, not electromagnetic waves, can give rise to the interference pattern seen in the two-slit experiment. They are shown to do so because the relevant quantum amplitude is a linear combination of two terms, leading to the pattern when neither slit is identified as the one the photon went through, but collapsing to one term and no pattern if the slit is identified. Similar results are shown to occur when individual electrons are incident on the two slits, and when large molecules, which have de Broglie wavelengths, are scattered by diffraction gratings. Many other interference experiments are described, including those where a photon was shown to be in two places simultaneously and one where a photon displayed both wave and particle features.
In the early 1900s more and more experimental evidence was accumulated indicating that microscopic particles show wave-like properties in certain situations. These particle-wave features are very evident, e.g., in measurements where electrons are diffracted from a double slit to propagate toward a screen where they are detected. Based on the classical averaging of particles discussed in Section 1.2.2, one expects that the double slit only modulates the overall intensity, not the spatial distribution. Experimentally, however, one observes a nearly perfect interference pattern at the screen implying that the electrons exhibit wave averaging features such as discussed in Section 2.1.2. This behavior, originally unexpected for particle beams, persists even if the experiment is repeated such that only one electron at a time passes the double slit before it propagates to the detection screen. Thus, the wave aspect must be an inherent property of individual electrons and not an ensemble effect. Another, independent argument for the failure of classical physics is that the electromagnetic analysis of atoms leads to the conclusion that the negatively charged electron(s) should collapse into the positively charged ion because the electron–ion system loses its energy due to the emission of radiation. As we will see, this problem can be solved by including the wave aspects of particles into the analysis. In particular, as discussed in Section 2.3.3, waves can never be localized to a point without increasing their momentum and energy beyond bounds.
Abstract: Many problems exist in the Double Slit Experiment when you consider that the elements in the test are moving as waves. Outside of the pattern resembling peeks and troughs that overlap each other; there is no real scientific explanation on how this is taking place. In a more accurate and classical way, can we explain how the dark and light areas of the interference pattern are being made? Why is an Interference pattern being made when particles are being sent through the exercise one at a time? And how is it that through observation the Interference pattern collapses in on itself. Waves add more questions than they do answers, a very typical outcome of an incorrect solution. Maybe the unanswered questions left behind by the wave theory is a confirmation of its inaccuracy and not the mystique of its results. Rather than double down on the wave theory with time traveling particles, elements of duality, and the Copenhagen Interpretation; l reconsidered that elements tested in the double slit experiment behave as particles. But this time, I weighed the thought that these bits of matter are much smaller than previously thought. This new logic allowed particles with straight trajectories to interact with the edge of materials used in the double slit wall in a very detailed way. This created a storm of new ways to look at what is really taking place in the test; revealing the competence of the detectors utilized and the capacity of the Nonlinear Optical Crystal. Everything solved from just one idea, that quantum move as particles but on a much smaller scale. This is the enigma of the Double Slit Experiment.
The discovery of the electron and its strange properties is the cornerstone of quantum mechanics. Based on their spin properties, photons and electrons, now categorized as fermions and bosons under the Standard Model, exhibit an enigmatic dual nature of wave and particle. This property, the interpretation of which is still debated today, is supported by various experiments, as we saw in Chap. 4 . One of these, in particular, can be considered the basis of any interpretative model on the dual nature of photons and electrons, the double-slit experiment. This experiment will lead to the famous Copenhagen interpretation, which is still a key to explain quantum mechanics today. With all its incredible weirdness, the double-slit experiment is thus the basis of quantum mechanics, as we shall see in this chapter. Experiments and interpretations of the strange quantum properties of the electron have also led to the discovery of other physical phenomena seemingly impossible according to classical physics, such as the tunnel effect and quantum entanglement. These phenomena have no classical equivalent and can be explained only by resorting to quantum properties of electrons.
Young’s double-slit experiment played a crucial role in establishing the wave nature of light. In this chapter, the shocking result that incident electrons yield a similar interference pattern as that formed by light waves is described. It is shown that the only way the experimental results could be explained is via a wave function description of electrons. It is also shown that, in the same experiment, the interference fringes disappear if the which-path information becomes available. This is the essence of wave–particle duality. The first of the Einstein–Bohr debates on wave-particle duality and Bohr’s principle of complementarity in the double-slit experiment is also discussed. Also presented are the counterintuitive notions of delayed choice and quantum eraser effects showing how the availability or erasure of information generated in the future can affect how the data in the present can be interpreted.
Abstract Young’s double-slit experiment played a crucial role in establishing the wave nature of light. In this chapter, the shocking result that incident electrons yield a similar interference pattern as that formed by light waves is described. It is shown that the only way the experimental results could be explained is via a wavefunction description of electrons. It is also shown that the interference fringes disappear if the which-path information becomes available. This is the essence of wave–particle duality. The first of the Einstein–Bohr debates on wave–particle duality and Bohr’s principle of complementarity in the double-slit experiment are also discussed. The counterintuitive notions of delayed choice and quantum eraser effects showing how the availability or erasure of information generated in the future can affect how the data in the present can be interpreted are presented. Quantum interference is responsible for novel phenomena like interaction-free measurement and counterfactual communication.