Deciphering the Enigma of Wave-Particle Duality Mani L. Bhaumik Department of Physics and Astronomy, University of California, Los Angeles, USA E-mail: [email protected] Editors: Zvi Bern & Danko Georgiev Article history: Submitted on October 17, 2016; Accepted on November 28, 2016; Published on December 7, 2016. satisfactory explanation of the confounding 1 Introduction wave-particle duality of matter is presented in Aterms of the reality of the wave nature of a par- Ever since the advent of the wildly successful quantum ticle. In this view, a quantum particle is an objectively theory nearly a century ago, its antecedent, wherein the real wave packet consisting of irregular disturbances wave aspect is always associated with a particle has been of underlying quantum fields. It travels holistically a source of great mystery to professional scientists and as a unit and thereby acts as a particle. Only the to- to the public as well. Louis de Broglie, who offered the tality of the entire wave packet at any instance em- hypothesis, considered the wave to be a fictitious pilot bodies all the conserved quantities, for example the wave that guides a particle. Almost a quarter of a century energy-momentum, rest mass, and charge of the par- later, David Bohm came up with the notion of a quantum ticle, and as such must be acquired all at once during potential instead, providing the quantum wave that guides detection. On this basis, many of the bizarre behav- the classical particle. He never expounded, however, on iors observed in the quantum domain, such as wave the source of energy of the quantum potential. Nonethe- function collapse, the limitation of prediction to only less, due to other appealing aspects of Bohm’s theory a probability rather than an actuality, the apparent such as the introduction of the concept of nonlocality, a simultaneous existence of a particle in more than one small segment of the scientific community still seem to place, and the inherent uncertainty can be reasonably grant it credence. comprehended. The necessity of acquiring the wave Niels Bohr, the principal architect of the Copenhagen function in its entirety for detection, as evinced by interpretation, was content to accept the duality paradox the appearance of collapse of the wave function, sup- as an elementary aspect of the natural world. In his view, ports the paradigm of reality of the wave function de- a quantum object will exhibit its wave aspect at some scribed here. times and its particle nature at others, depending on the Quanta 2016; 5: 93–100. circumstances. He considered such duality an essential feature of complementarity, which he presumed to be an inherent property of nature. During all this time, buoyed by the phenomenal suc- cess and the superb predictive power of the quantum theory, most practicing physicists avoided the conundrum This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY-3.0, which by treating the wave function as merely a fictitious math- permits unrestricted use, distribution, and reproduction in any medium, ematical construct to be used for the algorithm called provided the original author and source are credited. quantum theory. Quanta j DOI: 10.12743/quanta.v5i1.54 November 2016 j Volume 5 j Issue 1 j Page 93 This caused the pioneering proponent of the quantum effect in 1923. The following year, de Broglie extended theory, Albert Einstein, great consternation. He posited, the idea of wave-particle duality to matter particles with “This double nature of radiation (and of material corpus- enthusiastic support from Einstein. cles) ::: has been interpreted by quantum-mechanics in Soon the evidence for the matter wave came along an ingenious and amazingly successful fashion. This in- with the apparent accidental discovery of electron waves terpretation ::: appears to me as only a temporary way by Clinton Davisson and Lester Germer in observing out :::” [1, p. 51] a diffraction pattern in the beam of electrons scattered “At the heart of the problem,” Einstein said of quantum by nickel crystal [8]. Shortly before that, George Paget mechanics, “is not so much the question of causality but Thomson and Alexander Reid also provided some evi- the question of realism.” [2, p. 460] Einstein’s insistence dence of matter waves by detecting a diffraction pattern on the reality of the wave function, however, remained when electrons passed through a very thin metallic foil [9]. conspicuously dormant until recently, when it became Both Davisson and Thompson shared the 1937 Nobel the subject of lively discussion in the form of -ontic Prize in Physics for their startling discovery, ushering the versus -epistemic debate. A comprehensive review has age of quantum physics in earnest. been provided by Leifer [3]. It would appear that -ontic In the meantime Erwin Schrodinger,¨ inspired by de theories advanced by Colbeck and Renner [4] and Pusey, Broglie and Einstein, formulated the wave mechanics Barrett, and Rudolph [5], which advocate the objective of quantum physics, replacing the particle in classical reality of the wave function, are gaining more traction. mechanics with a wave function [10]. Their presentation, however, is based primarily on an information-theoretic viewpoint and does not take into ac- count physical aspects such as the conservation of energy 2 Reality of the wave function or momentum. In this work, we provide a paradigm of the reality of the In previous work [11], we presented a credible argument wave function based on energy-momentum considerations in favor of the existence of an objective reality behind that cogently explicates the enigma of the wave-particle the wave function at the core of quantum physics. A duality, an enigma which is inseparably connected with synopsis is presented here. The ontology of the wave several other conundrums of quantum physics, such as, function advocated in this paper is primarily grounded on Heisenberg’s uncertainty principle, the Born rule of prob- the incontrovertible physical evidence that all electrons ability, collapse of the wave function, and the apparent in the universe are exactly identical. simultaneous existence of a particle in more than one The answer to the long standing puzzle of why all elec- place. The concept of the objective reality presented here trons in all respects are universally identical, a feature solely in terms of physical parameters is more explicit, eventually found to be true as well of all the other fun- albeit for a single particle, and ought to harmonize with damental particles, was finally provided by the quantum the information-theoretic approach. field theory of the Standard Model of particle physics The topic of wave-particle duality itself has a fascinat- constructed by combining Einstein’s special theory of rel- ing history. Notably, it was Einstein himself who fostered ativity with quantum physics, a science which has evolved this innovative notion by advocating the real existence from his own pioneering contributions. of quanta of radiation or photons. Previously Maxwell Nobel Laureate in Physics, Steven Weinberg [12], de- and others had convincingly established the wave nature clares that quantum field theory is an unavoidable conse- of electromagnetic radiation. An abundance of experi- quence of the reconciliation of quantum mechanics with ments on the interference, diffraction, and scattering of special relativity. It has successfully explained almost light had substantiated it beyond any reasonable doubt. all experimental observations in particle physics and cor- Thus, it was greeted with utter shock and disbelief when rectly predicted a wide assortment of phenomena with Einstein argued in 1905 that under certain circumstances impeccable precision. By way of many experiments over light behaves not as continuous waves but as discontinu- the years, the quantum field theory of Standard Model ous, individual particles [6,7]. These particles, or “light has become recognized as a well-established theory of quanta,” each carried a “quantum,” or fixed amount, of physics. Another Nobel Laureate David Gross asserts energy. that all the pieces of the puzzle of the Standard Model In the face of the almost unanimous opposition of his of particles physics fit beautifully in quantum field the- peers, Einstein remained perhaps the principal champion ory of the Standard Model such that there are no more of the wave-particle duality of radiation for almost two pieces of the puzzle left to fit (private communication). decades, until he was finally vindicated by the spectac- Yet another Physics Nobel Laureate, Franck Wilczek un- ular observation of the particle aspect in the Compton derscores, “the standard model is very successful in de- Quanta j DOI: 10.12743/quanta.v5i1.54 November 2016 j Volume 5 j Issue 1 j Page 94 scribing reality—the reality we find ourselves inhabit- When an electron is created instantaneously from the ing” [13, p. 96]. Expressions of such confidence encour- electron quantum field, its position would be indefinite age us to anchor our reliance on it. since a regular ripple with a very well defined energy Although one might argue that the Standard Model and momentum is represented by a non-localized peri- accurately describes the phenomena within its domain, odic function. However, the moment the electron comes it is still incomplete as it does not include gravity, dark into existence, quantum fluctuations facilitate its inter- matter, dark energy, and other phenomena. However, action with all the other quantum fields. For example, because of its astonishing success so far, whatever deeper the presence of the electron creates a disturbance in the physics may be necessary for its completion would very electromagnetic or the photon quantum field. Assisted by likely extend its scope without repudiating its current a fleeting quantum fluctuation, the disturbance in the pho- depiction of fundamental reality.