concept is one of the most debated issues in the history of physical science. Some thirty years ago, we published an article in Physics Today entitled The Concept of the Photon, 1 in which we described the photon as a classical electromagnetic field plus the fluctuations associated with the vacuum. However, subsequent developments required us to envision the as an intrinsically quantum mechanical entity, whose basic physics is much deeper than can be explained by the simple 'classical wave plus vacuum fluctuations' picture. These ideas and the extensions of our conceptual understanding are discussed in detail in our recent quantum optics book. 2 In this article we revisit the concept based on examples from these sources and more.
concept is one of the most debated issues in the history of physical science. Some thirty years ago, we published an article in Physics Today entitled The Concept of the Photon, 1 in which we described the photon as a classical electromagnetic field plus the fluctuations associated with the vacuum. However, subsequent developments required us to envision the as an intrinsically quantum mechanical entity, whose basic physics is much deeper than can be explained by the simple 'classical wave plus vacuum fluctuations' picture. These ideas and the extensions of our conceptual understanding are discussed in detail in our recent quantum optics book. 2 In this article we revisit the concept based on examples from these sources and more.
Focusing on the unresolved debate between Newton and Huygens from 300 years ago, The Nature of Light: What is a Photon? discusses the reality behind enigmatic photons. It explores the fundamental issues pertaining to light that still exist today. Gathering contributions from globally recognized specialists in electrodynamics and quantum optics, the book begins by clearly presenting the mainstream view of the nature of light and photons. It then provides a new and challenging scientific epistemology that explains how to overcome the prevailing paradoxes and confusions arising from the accepted definition of a photon as a monochromatic Fourier mode of the vacuum. The book concludes with an array of experiments that demonstrate the innovative thinking needed to examine the wave-particle duality of photons. Looking at photons from both mainstream and out-of-box viewpoints, this volume is sure to inspire the next generation of quantum optics scientists and engineers to go beyond the Copenhagen interpretation and formulate new conceptual ideas about light-matter interactions and substantiate them through inventive applications.
The idea of the photon has stirred the imaginations of physicists ever since 1905 when Einstein originally proposed the use of light quanta to explain the photoelectric effect. This concept is formalized in the quantum theory of radiation, which has had unfailing success in explaining the interaction of electromagnetic radiation with matter, seemingly limited only by the ability of physicists to perform the indicated calculations. Nevertheless, it has its conceptual problems—various infinities and frequent misinterpretations. Consequently an increasing number of workers are asking, “to what extent is the quantized field really necessary and useful?” In fact the experimental results of the photoelectric effect were explained by G. Wentzel in 1927 without the quantum theory of radiation. Similarly most electro-optic phenomena such as stimulated emission, reaction of the emitted field on the emitting atom, resonance fluorescence, and so on, do not require the quantization of the field for their explanation. As we will see, these processes can all be quantitatively explained and physically understood in terms of the semiclassical theory of the matter–field interaction in which the electric field is treated classically while the atoms obey the laws of quantum mechanics. The quantized field is fundamentally required for accurate descriptions of certain processes involving fluctuations in the electromagnetic field: for example, spontaneous emission, the Lamb shift, the anomalous magnetic moment of the electron, and certain aspects of blackbody radiation. (The Compton effect also fits here, but see later under references 8b and c.) Here we will outline how the photon concept originated and developed, where it is not required and is often misused, and finally where it plays an essential role in the understanding of physical phenomena. In our discussion we will attempt to give a logically consistent definition of the word “photon”—a statement far more necessary than one might think, for so many contradictory uses exist of this elusive beast. In particular consider the original coining of the word by G. N. Lewis: “[because it appears to spend] only a minute fraction of its existence as a carrier of radiant energy, while the rest of the time it remains an important structural element within the atom…, I therefore take the liberty of proposing for this hypothetical new atom which is not light but plays an essential part in every process of radiation, the name photon!” (our exclamation point). Clearly the present usage of the word is very different.
A richly diverse range of phenomena and applications, frequently in the context of laser applications, owe their means of operation to the properties of the photon. Yet, since the arrival of the laser, the distinctive and often paradoxical nature of the photon has become more than ever evident, and what the optics community now understands by a ‘photon’ has become richer – certainly less simple, than Einstein’s original conception. There has been a marked expansion in the pace of development since the now familiar derivative term ‘photonics’ first emerged, and in much current theory any dividing line between ‘real’ and ‘virtual’ photons proves to be illusory. So if, in this technical sense, no photon can ever be regarded as entirely real, one is drawn to deeper questions of whether the photon is ‘real’ in the broader sense of reality. Some would argue that electromagnetic fields are closer to irreducible reality. Yet whether we elect to describe optical phenomena in terms of fields or photons, neither represents what is actually measured. The surest ground has to be found where theory is cast in terms that explain or predict actual observations, under given conditions. It is consistent with the path integral formulation of quantum mechanics that derivations should not prescribe what intervenes between setup and measurement, but instead allow for all possibilities. Indeed, one of the beauties of the associated mathematics is its capacity to home in on possibilities that most closely conform to post-event physical interpretation. Still, we can ask: how much do or can we know about the photon itself? How much information could this entity contain or convey? And, how essential is a photonic formulation of theory? This study focuses on some of the key issues.
Light occupies a special position in our attempts to understand nature both classically and quantum mechanically. We recall that Newton, who made so many fundamental contributions to optics, championed a particle description of light and was not favorably disposed to the wave picture of light. However, the beautiful unification of electricity and magnetism achieved by Maxwell clearly showed that light was properly understood as the wave-like undulations of electric and magnetic fields propagating through space. The central role of light in marking the frontiers of physics continues on into the twentieth century with the ultraviolet catastrophe associated with black-body radiation on the one hand and the photoelectric effect on the other. Indeed, it was here that the era of quantum mechanics was initiated with Planck's introduction of the quantum of action that was necessary to explain the black-body radiation spectrum. The extension of these ideas led Einstein to explain the photoelectric effect, and to introduce the photon concept. It was, however, left to Dirac to combine the wave-and particlelike aspects of light so that the radiation field is capable of explaining all interference phenomena and yet shows the excitation of a specific atom located along a wave front absorbing one photon of energy. In this chapter, following Dirac, we associate each mode of the radiation field with a quantized simple harmonic oscillator, this is the essence of the quantum theory of radiation.
Our early training in physics encourages us to imagine photons as little pellets flying through the air, and to see wave-particle duality as a paradox. This view persists from the debates on quantum mechanics early in the 20th century. Much has happened in the past 80 years, however. Quantum optics and field theory have developed a very sophisticated mathematical formalism for treating photons, and this formalism affects how we view photons. Recently, physicist Carver Mead of Cal Tech published a book with a very persuasive mathematical argument of how to understand quantum jumps. He also argued that photons are not "real." In this talk, I will present, using only basic algebra, the main points of quantum optics and Carver Mead's view. These results also lead to a reconsideration of the EPR paradox.
In the mid-18th century, Isaac Newton regarded light as some extremely small particles. Based on this, Newton established the particle theory of light. In the mid-19th century, Huygens and Augustine Jean Fresnel conducted extensive research on light and concluded that light is a wave. Afterwards, Maxwell proposed the theory of electromagnetism. Maxwell believed that light is a wave with a wavelength within a limited range. With the establishment of Maxwell's equation electromagnetic wave theory, the wave nature of light began to dominate the mainstream consciousness; However, in the late 19th century, a series of experimental phenomena represented by the photoelectric effect could not be accurately explained by the wave theory of light. In 1905, Einstein proposed the concept of light quanta and successfully explained the photoelectric effect. While perfectly explaining these issues, a new question arises: what is the essence of light, given that both particle and wave properties can accurately reflect certain properties of light? It has always been the most fiercely debated issue in the history of optics. Einstein said that we are not yet clear about what light quanta are, and wave particle duality cannot fully explain optical phenomena. Based on the study of Albert Einstein's concept of quanta light, wave particle duality of light, string theory, and optical frequency combs, the author proposes the concept of lightstring, attempting to propose new ideas for studying the essence of light and its generation mechanism. Siwen Bi has been researching quantum remote sensing since March 2000 and quantum spectral imaging since June 2003, but has encountered some difficulties and problems. What is the basic theory of passive imaging in quantum remote sensing? How is technology implemented? What is the fundamental theory of quantum spectroscopy? The Implementation Technology of Quantum Optical Field Entangled States in Long Distance Quantum Detection Process? These difficulties and questions prompt the author of this article to contemplate and study the essence of light? What is the fundamental theory of the future technology of quantum optics? Siwen Bi conducted exploratory research on the nature of light in 2006. This article first provides an overview of the development history and research status of optics and describes the difficulties and shortcomings in fully explaining optical phenomena due to the wave particle duality of light quantum and light; Then, two inspiring viewpoints on optical frequency comb and chord theory were introduced. On this basis, the basic concept of optical string (optical frequency string), the prototype description of optical string, the mechanism of optical string generation, and the discussion of Lightstring, generation process are proposed and emphasized; Proposed the mechanism of string light effect. Published On Two Heuristic Viewpoints Concerning the Study of Light (October 13-15, 2014), New Viewpoints In Light Quantum Research: Lightstring (2016), Discuss wave-particle duality of light, (February 28, 2017), and an Exploratory research on the light quantum future technical basis (February 1, 2019). Over the past 17 years, achieved some original and innovative research results. some original innovative research achievements have been achieved. Received high praise from international scholars and professors, such as the American Journal of Physics and Applications, which sent me a congratulatory letter saying, "Dear Bi Siwen, Warmest greeting from the Editorial Department! It is reported that at the International conference on photo and optical Engineering (ICPOE 2014), a paper entitled" Two Enlightening Views on Optical Research "was published, and the theme of the paper impressed us deeply. It has attracted the attention of Photon researchers and Scholars ...Your research is highly appreciated by us … " And invite Professor Bi Siwen as a paper reviewer for the American Journal of Physics and Applications. I have received the paper review certificate, dated May 25th, 2018. Based on the above research, Siwen Bi elaborated on the geometric and kinematic characteristics of Lightstring, and proposed the essence of light based on the concept of Lightstring, in order to concretize the concept of light quanta. On this basis, the mechanism of string light effect based on the concept of optical string is proposed. An attempt has been made to further study the quantum and wave particle duality of light, gain a profound understanding of the nature of light, and answer the question "What is light?" by proposing a new approach and method for studying the nature of light and its generation mechanism. Proposed a study on optical quantum; The wave particle duality of light; New ideas, methods, and perspectives on the mechanism of light generation.