This paper summarizes our papers over the past years which – taken together – effectively amount to a classical interpretation of QED. Our very first paper started exploring a basic intuition: if QED is the theory of electrons and photons, and their interactions, then why is there no good model of what electrons and photons actually are? We have tried to address this perceived gap in the theory – further building on the Zitterbewegung model of an electron – ever since. We thought we should write one final paper to provide some history – acknowledgements, basically – and summarize the key principles of the interpretation.
This paper summarizes our papers over the past years which – taken together – effectively amount to a classical interpretation of QED. Our very first paper started exploring a basic intuition: if QED is the theory of electrons and photons, and their interactions, then why is there no good model of what electrons and photons actually are? We have tried to address this perceived gap in the theory – further building on the Zitterbewegung model of an electron – ever since. We thought we should write one final paper to provide some history – acknowledgements, basically – and summarize the key principles of the interpretation.
This paper summarizes the basic principles of the common-sense interpretation of quantum physics that we have been exploring over the past few years. We also touch on some areas we did not explore before. We note, for example, that the ring current model of matter-particles must also come with a dynamic view of the fields surrounding charged particles. Potential barriers -or their corollary: potential wells – should, therefore, not be thought of as static fields: they vary in time. They result from two or more charges moving around and creating some joint or superposed field. Hence, a particle breaking through a ‘potential wall’ or coming out of a potential ‘well’ probably just uses an opening which corresponds to a classical trajectory. This should offer a new perspective on the foundations of quantum mechanics.
Quantum field theory, and in particular quantum electrodynamics (QED), are milestones in the history of twentieth century physics. Not all interpretative problems presented by them, however, can be said to have been settled once and for all. In this paper the first papers on QED by P. Jordan and P.A.M. Dirac are briefly analysed, with the intent to show that the authors confronted themselves from the beginning with the essential of those problems, that their answers were not unambiguous, and that there are still some open questions concerning the subject matter. The potentiality and up-to-dateness of Dirac's work are particularly emphasised.
In this paper, we try to show where and why quantum mechanics went wrong – and why and when the job of both the academic physicist as well as the would-be student of quantum mechanics turned into calculating rather than explaining what might or might not be happening. Modern quantum physicists effectively resemble econometrists modeling input-output relations: if they are lucky, they will get some kind of mathematical description of what goes in and what goes out, but the math does not tell them how stuff actually happens. To show what an actual explanation might look like, we bring the Zitterbewegung electron model and our photon model together to provide a classical explanation of Compton scattering of photons by electrons so as to show what electron-photon interference might actually be: two electromagnetic oscillations interfering (classically) with each other. While developing the model, we also offer some reflections on the nature of the Uncertainty Principle. Finally, we also offer a brief history of the bad ideas which led to the current mess in physics.
The Zitterbewegung model of an electron offers a classical interpretation for interference and diffraction of electrons. The idea is very intuitive because it incorporates John Wheeler’s idea of mass without mass: we have an indivisible naked charge that has no properties but its charge and its size (the classical electron radius) and it is easy to understand that the electromagnetic oscillation that keeps this tiny circular current going – like a perpetual current ring in some superconducting material – cannot be separated from it. In contrast, we keep wondering: what keeps a photon together? Hence, the real challenge for any realist interpretation of quantum mechanics is to explain the quantization of light: what are these photons? In this paper, we offer a classical quantum theory for light. The intuition behind the model is the same as the one we developed for an electron: we think of the photon as a harmonic electromagnetic oscillator, and its elementary cycle determines its properties, including spin and its size (the effective area of interference).
Abstract This book is unique in covering phenomena in photon- matter interactions in a unified way over a range of many orders in energy. The quantum field theoretic approach to the fully relativistic theory of quantum electrodynamics (QED) is presented together with the non- relativistic theory in both confined and unconfined geometries. The predictions of QED have been verified to a greater accuracy than any other physical theory. Moreover QED is a paradigm for other gauge theories and is presented in such a way that the generalisation to other gauge theories is natural. Gauge and Poincare symmetry properties and the non-existence of a photon wave function are thoroughly discussed. Starting from the Dirac equation the non-relativistic interaction of the electron with the electromagnetic field is derived as an effective Hamiltonian of multipole expansions. Much of quantum optics is based on the lowest order dipole approximation. From this point on the treatment of fully relativistic QED and quantum optics is done in parallel. Applications of perturbation theory such as Compton and Moller scattering and the theory photdetection are given. After the impressive successes of QED, the limitation of the theory and the necessity of electroweak theory and quantumchromodynamics are discussed. The remaining chapters are devoted to quantum optics inside cavaties. Various approaches to open systems such as master equations are discussed within the context of active systems (e.g. the laser) and passive systems. Semi- classical approximarions are shown to imply a rich non- linear dynamics including chaos for certain parameter regimes. The effect of fluctuations on such non-linear dynamics is also studied. The final chapter is devoted to highly non- classical states of the light field such as photon number, squeezed and two photon entangled states. The latter are studied for the important system of parametric down conversion and the localisation properties of photons are characterised in terms of asympotic tails in photodetection probabilities as a function of time delay. The range of the book has wider benefits. Workers in quantum optics will gain a deeper understanding of the foundations of their subject and field theorists will see concrete examples of open systems, which are beginning to impinge on fundamental theories.
During these three years we focused on several topics in quantum otpics and quantum electrodynamics. A central theme in our investigations is that of the photon wave function. Can quantum optics and quantum electrodynamics experiments be described simply, in position space, with the help of a wave function describing the photon(s) featured in the experiment ? The answer to that question is not quite obvious: the usual description of photons takes place in the reciprocal space of wave vectors. But these experiments call for a wave mechanical description in the position representation, as is done in quantum mechanics textbooks in situations featuring massive particles. Moreover, in a recent experiment [1], single photon trajectories through a Young two-slit setup have been observed. In order to try and describe these trajectories formally, it is natural to build a wave mechanical formalism for photons. We therefore studied in detail the formal construction of the photon wave function, an object which was little studied until the 1990s. We also studied the properties of the photon wave function in the presence of sources.To do that, we considered several open (interacting) quantum systems. We saw that there exists in principle an infinite number of possibilities when defining the photon wave function. We emphasised several criteria on the basis of which it appears that only three choices for the wave function are interesting. One of them coincides with an object introduced and used by Glauber [2] to study light detection andthe correlations of the electromagnetic field in the quantum regime. We also saw that, in the absence of sources, the propagation equation for a single photon is formally equivalent to Maxwell’s equations. At low photon numbers, the wave function formalism can be very useful. We adapted it to interacting systems,first, to cavity quantum electrodynamics (QED) [3], in particular to the experiments carried out by Serge Haroche’s group [4]. We proposed a simple model to describe photons in QED cavities. With this model, and with the helpof the photon wave function, we studied the propagation of photons escaping a cavity. We also constructed the Lindblad master equation without introducing nonunitary quantum jumps (also see [5]). We finally investigated the spacetime evolution of a photon which is emitted during the decay of an atomic electron. After having carefully studied the dynamics of the electronic decay, especially at very short times [6, 7], we set out to describe the emitted electromagnetic field as rigorously as possible. This emitted field, surprisingly, does not evolve causally. Though this is not entirely unexpected in view of Hegerfeldt’s theorem, which states [8] that causality is impossible for quantum systems which are described by a Hamiltonian with a spectrum which is bounded by below, we identified [9] two other sources of non causality. One of them was predicted qualitatively by Shirokov [10], while the other one, which is completely new as far as we can tell, is still to be better understood