The articles in this special section represent the second of a series that focus on quantum technologies. These articles bridge the gap between classical electromagnetics and quantum electromagnetics. The article “Quantum Maxwell’s Equations Made Simple,” by Chew et al., in particular, introduces quantum mechanics and how it relates to quantum electromagnetics.
The articles in this special section represent the second of a series that focus on quantum technologies. These articles bridge the gap between classical electromagnetics and quantum electromagnetics. The article “Quantum Maxwell’s Equations Made Simple,” by Chew et al., in particular, introduces quantum mechanics and how it relates to quantum electromagnetics.
The articles in this special section compare classical and quantum electromagnetics. The articles introduce the fundamental concepts of quantum electromagnetics and compares them to classical ones. When James Clerk Maxwell published his paper on those equations that bear his name, he could never have imagined that they would have such a wide-ranging impact. These equations are valid from static to X-ray, from subatomic length-scale to galactic length-scale, and also from classical electromagnetics to quantum electromagnetics (this includes quantum electrodynamics and quantum optics). The advent of one of the first computers by Google uses microwave photons, which have a much longer wavelength than do optical ones; therefore, much microwave/electromagnetic engineering is needed for designing many aspects of quantum technologies. Due to the ease of engineering at microwave frequencies because of the component sizes involved, many proof-of-concept works are done at microwave frequencies with well-established electromagnetic engineering.
Despite its successes, quantum mechanics (QM) has remained mysterious to all who have encountered it. Starting with Bohr and progressing into the present, the departure from intuitive, physical reality has widened. The connection between QM and reality is more than just a “philosophical” issue. It reveals that QM is not a correct or complete theory of the physical world and that inescapable internal inconsistencies and incongruities arise when attempts are made to treat it as physical as opposed to a purely mathematical “tool.” Some of these issues are discussed in a review by F. Laloe [Am. J. Phys. 69, 655 (2001)]. In an attempt to provide some physical insight into atomic problems and starting with the same essential physics as Bohr of e moving in the Coulombic field of the proton and the wave equation as modified by Schrodinger, a classical approach is explored that yields a remarkably accurate model and provides insight into physics on the atomic level. The proverbial view, deeply seated in the wave-particle duality notion, that there is no large-scale physical counterpart to the nature of the electron may not be correct. Physical laws and intuition may be restored when dealing with the wave equation and quantummechanical problems. Specifically, a theory of classical quantum mechanics (CQM) is derived from first principles that successfully applies physical laws on all scales. Rather than using the postulated Schrodinger boundary condition “Ψ → 0 as r → ∞,” which leads to a purely mathematical model of the electron, the constraint is based on experimental observation. Using Maxwell’s equations, the classical wave equation is solved with the constraint that the bound (n = 1)state electron cannot radiate energy. By further application of Maxwell’s equations to electromagnetic and gravitational fields at particle production, the Schwarzschild metric is derived from the classical wave equation, which modifies general relativity to include conservation of spacetime in addition to momentum and matter/energy. The result gives a natural relationship among Maxwell’s equations, special relativity, and general relativity. CQM holds over a scale of spacetime of 85 orders of magnitude — it correctly predicts the nature of the universe from the scale of the quarks to that of the cosmos. A review is given by G. Landvogt [Internat. J. Hydrogen Energy 28, 1155 (2003)].
The free electron is undoubtedly an electromagnetic particle. However, the fundamental equations describing the free electron in quantum mechanics do not account for its electromagnetic properties; instead, they are based solely on its mechanical characteristics. Such treatment is insufficient for a complete description. In conventional quantum mechanics, the free-electron Schrödinger equation remains unrelated to Maxwell's differential equations. By considering the electron as both a quantum mechanical oscillator and a quantum electrodynamic oscillator, it becomes possible to derive the free-electron Schrödinger equation directly from Maxwell's equations. This article presents a novel theoretical approach to treating the electron, providing a simple and transparent derivation that, to the best of our knowledge, has not yet been published in the literature.
The article “Quantum Radars and Lidars: Concepts, Realizations, and Perspectives,” by Gregory Slepyan, Svetlana Vlasenko, Dmitri Mogilevtsev, and Amir Boag is one that stretches the imaginations of conventional practitioners of radar technology. The quantum advantage that quantum sensing will deliver is too great to be ignored, even though naysayers may not agree on this path. Also, the knowledge base in quantum technologies is incredibly thin, and, hopefully, this article will spur more engineers and scientists to take up the challenge of working in this area, sharing their experience and knowhow as well as expanding the knowledge base. We have seen the recent exciting growth in quantum computing technology, and we wish for the same excitement in quantum sensing technology. The ability to use entangled photon pairs to enhance the detection of weak photons will be beneficial to other applications, such as quantum sensing and quantum imaging in biomedical engineering and health care. Entangled photon pairs are also useful in quantum communication.
Quantization of the electromagnetic field (called quantum electromagnetics here) has been a fascinating and important subject since its introduction by Dirac in 1927. However, this knowledge is often inaccessible to technologists such as engineers. This subject will be discussed in its simplest terms so that it can be easily understood by a larger community of researchers. To this end, a new way of motivating Hamiltonian mechanics is presented. Furthermore, a novel way of deriving the quantum equations of motion for electromagnetics and Maxwell's equations is presented.
The quantum technologies series of articles started with the basics of quantum electromagnetics and then turned to deal with various promising applications. These range from the computation of the Casimir force to the analysis of interactions between electromagnetic waves and large molecules behaving as nanoantennas. Another article outlined the advantages of more futuristic higher level applications, such as quantum radars and lidars. Recent articles in the series covered device-level performance, including the quantum electrodynamics of plasmonic waveguides and construction of transmon qubits. Similarly, the present contribution, “Numerical Simulations of Laser Pulse Propagation in Quantum Active Media,” deals with the semiclassical analysis of field interaction with a collection of quantum dots, posing a heavy computational challenge. One typically sidesteps this by deriving a homogeneous behavior. But this leaves out interesting design opportunities. This article takes a different approach to the self-consistent analysis of a large ensemble of quantum dots. It combines analysis methods that are well known in the electromagnetics community together with predictor–corrector methods to solve for the evolution of the polarization of quantum dots. Interestingly, the approach correctly predicts experimentally observed behavior.