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On the logic resolution of the wave particle duality paradox in quantum mechanics (Extended abstract) M.A. Nait Abdallah To cite this version: M.A. Nait Abdallah. On the logic resolution of the wave particle duality paradox in quantum me- chanics (Extended abstract). 2016. hal-01303223 HAL Id: hal-01303223 https://hal.archives-ouvertes.fr/hal-01303223 Preprint submitted on 18 Apr 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. On the logic resolution of the wave particle duality paradox in quantum mechanics (Extended abstract) M.A. Nait Abdallah UWO, London, Canada and INRIA, Paris, France Abstract. In this paper, we consider three landmark experiments of quantum physics and discuss the related wave particle duality paradox. We present a formalization, in terms of formal logic, of single photon self- interference. We show that the wave particle duality paradox appears, from the logic point of view, in the form of two distinct fallacies: the hard information fallacy and the exhaustive disjunction fallacy. We show that each fallacy points out some fundamental aspect of quantum physical systems and we present a logic solution to the paradox. 1 Introduction It is a common view among physicists to see Quantum Mechanics simply as a calculation method which yields results that are in astonishing accordance with all experimental observations performed so far. Under such a view, the math- ematical theory of Quantum Mechanics does not operate on mathematical ob- jects directly representing quantum physical objects, but rather on probabilities yielding useful pragmatic results. The question arises as to whether a more analytic mathematical approach to the study of quantum mechanics would be of some use, or even at all possible. In this paper, we explore, from the point of view of mathematics, the logical content of three major experiments due to Grangier, Roger and Aspect [11] and Scully, Englert and Walther [14], and draw from this analysis a logic-based solution to the wave particle duality paradox in Quantum Mechanics. 1.1 Three quantum physics experiments In reference [11] the authors describe two experiments that indisputably show that the light quantum, or photon, is both a wave and a particle. Such a simulta- neous double identity is very difficult to grasp within a classical logic conceptual framework, where it indeed leads to a paradox. The setup of Grangier et al. experiment #1 (Figure 1) has a light source that emits single photons, one by one, well-separated in time, and sends them through a beam splitter (half-silvered mirror). The emitted photons all have exactly the same physical properties. The intensity of light (luminous flow) thus emitted is evenly split by the half-slivered mirror, between a vertically reflected portion 2 M.A. Nait Abdallah and a horizontally transmitted portion. One positions a detector on each of the two exit channels, as well as a joint detection device at the end of both channels. Fig. 1. Grangier et al. First experiment Experiment # 2 setup (Figure 2) recombines both beams of light with a sec- ond beam splitter, thus yielding a Mach-Zehnder interferometer, where M1;M2 Fig. 2. Grangier et al. Second experiment are mirrors and BSin, Bout are beam splitters. Again, the intensity of light traveling the lower (resp. upper) path into the second beam splitter BSout is evenly split by the half-slivered mirror, between a horizontally reflected (resp. transmitted) portion and a vertically transmitted (resp. reflected) portion. The first experiment (Figure 1) shows that every single photon is detected by a single detector on a single path. The photons are not split on a beam splitter, each photon is insecable and can take only one of either path. Whence each single photon obviously behaves as a particle. In the second experiment (Figure 2), every single photon is detected as a single particle by a single end detector. However, every photon registers at hor- izontal end detector C, and none registers at vertical end detector D, thus dis- playing an interference fringe. Thus, light emitted by the single photon source, at discrete points in time, behaves like a wave. The electromagnetic field is co- herently split on a beam splitter, where \coherent" means that the two subwaves On the resolution of the wave particle duality paradox 3 (Huygens principle) have a constant phase difference (equal to π in this case.) One observes an interference fringe i.e., the photon behaves like a wave. Since at each beam splitter the photon has an equal chance to be reflected or transmitted, it should randomly register with equal probability at one end detector or the other. On the contrary, Grangier et al. experiment #2 demon- strates that probabilities associated with each path do not add up, all photons go to one detector only. From the point of view of probabilities, the quantum phenomenon does not decompose into a statistical distribution in a space of classical phenomena as in e.g., thermodynamics. Thus, the very same photon, upon traversing the first beam-splitter, behaves as a particle or as a wave, depending on which devices are to be found long after it has traveled through this beam splitter. How can the single photon be both split (i.e., a wave) and insecable (i.e., a particle) at the same time? This seemingly contradictory situation is the Wave Particle Duality Paradox and is one of the fundamental problems of Quantum Mechanics. One problem with the photon is that as a light quantum it vanishes upon detection. An third experiment, clarifying this matter, is Scully et al. experiment [14] which, instead of photons, uses excited atoms as particles. A microwave cavity, finely tuned on an atomic transition, is positioned on each channel of a Young slit interference experimental device. Atoms are first brought to an excited state using a laser beam, and then sent through the setup. Upon traveling through the cavities, the excited atom returns to its ground state, emitting one single photon. That photon remains trapped in the cavity. The presence of the photon in one of the cavities characterizes the path taken by the atom, thus providing which-way information and at the same time erasing the interference fringes i.e., making the wave-like behaviour of the atom disappear. Scully et al. experiment shows that the wave behaviour and the particle behaviour of the atom cannot be observed simultaneously: the physical availability of which- path information (particle behaviour) and the occurrence of interference (wave behaviour) are mutually exclusive. According to Feynman [10], p. 1-1, the wave particle duality phenomenon \has in it the heart of quantum mechanics; in reality, it contains the only mys- tery" of the theory \which cannot be explained in any classical way." 1.2 Notations Before we get to the heart of the matter, let us define some notations. The basic experimental setup of Grangier et al. experiment #2 is a Mach-Zehnder interferometer. It is constituted (Figure 3) of a single photon light source e, two half-silvered mirrors (beam splitters) B1;B2, two mirrors M1;M2, and two de- tectors C; D positioned on a rectangle as shown. The mirrors and beam splitters are oriented diagonally, the first beam splitter silvered face upward, the second beam splitter face down. 4 M.A. Nait Abdallah Fig. 3. Mach-Zehnder interferometer Each photon emitted at source e registers either at detector C or at detector D. Experiment shows that detection frequencies PC and PD are given by PC = 1 PD = 0 (1) Every photon emitted at e registers at detector C (constructive interference) and none at D (destructive interference). Define propositional formulae: a := \the photon takes the upper path a," b := \the photon takes the lower path b," i := \there is interference of probability waves." Such definitions implicitly assume that formulae a; b; i; : : : i.e., phrases such as \the photon takes the upper path" have a clear and unambiguous meaning. Given the propositional nature of the alphabet fa; b; i; : : :g thus chosen, we shall use propositional logic throughout this paper. Using these definitions, the experimental results [11, 14] reviewed above read as follows. (For reasons that will become clear later, the corresponding propo- sitional formulae are labeled using object variables belonging to some set V = fz; t; f; g; : : :g.) { Grangier et al. experiment #1: Upon leaving the first beam splitter, the photon traverses the a path or the b path z : a _ b (2) and there is never joint detection. In (2) expression z : a _ b means \z is a label of formula a _ b." In that expression, z 2 V is a variable used as a label for bookkeeping purposes, colon \:" is the labeling operation, and a; b are defined above. Labeling conventions are the same in (3) through (5) below. A deeper meaning of this seemingly innocuous labeling device will be revealed by Curry-Howard correspondence in Section 2.2, p. 10, where z : a_b will become an \inhabitation claim" and z an \inhabitant" of formula a _ b. For the time being, we can safely ignore this, and see it as a simple bookkeeping notational convention. On the resolution of the wave particle duality paradox 5 { Grangier et al.
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