Quantum electrodynamics of localized light

E. C. G. Sudarshan

Zhang, Fan, Lingxiao Shan, Juanjuan Ren +5 more

Cavity quantum electrodynamics studies light-matter interactions at single quanta level. Chiral photon-emitter coupling in photonic structures is characterized as unidirectional propagation locked by the local polarization of light. However, to realize the strong interaction of photon-emitter with direction-locked propagation, which will bring novel applications in nonreciprocal quantum devices, has not been reported yet. Here, we propose the coupled photonic crystal and metallic nanoparticle structure, where through strong local field with high helicity, the rate of circularly polarized photons emitting into photonic crystal waveguide is one order larger than that without the nanoparticle and the linewidth of Rabi splitting spectra is about one-tenth of that with only the nanoparticle, both with $\sim$ 95$\%$ photons propagating unidirectionally, which can be utilized in directional quantum light sources.

R. Loudon

M. I. Shirokov

The fulfillment in quantum electrodynamics of the principle of relativistic causality—the signal velocity does not exceed the velocity of light—is discussed. In Sec. 1 it is argued that this principle is not guaranteed automatically merely by the local commutativity of the theory. Section 2 is a critical review of the signal transmission problems which have been formulated and solved in the literature. In Sec. 3, this problem is considered in the framework of a simple but fairly realistic model of quantum electrodynamics. The signal source is an external current localized in some region S. The arrival of a signal in a region D at a distance R is established by a change in the coordinate, momentum, or energy of a charged particle. It is shown that proof of relativistic causality of the theory requires one to take into account appropriately quantum-mechanical and, in particular, quantum-electrodynamical features of the problem. In the final fourth section, a general formulation and exact solution of the signal transmission problem are given. The treatment is of sufficient generality for one to be able to assert that in the framework of quantum electrodynamics none of the possible methods of signal transmission violate relativistic causality.

Luka Gluvić

This work develops a structural framework in which light is understood not as a propagating particle or wave, but as a process of electromagnetic field reorganization constrained by geometry and material conditions.Emission is treated as a local disruption of field coherence rather than the creation of a traveling entity. Between emission and absorption, the field enters an open, pre-realizational phase in which no localized physical event occurs. Geometry, material boundaries, and environmental structure act as physical selectors that restrict admissible field configurations. A photon is realized only at absorption, as the localized closure of this open field organization.The framework integrates established empirical phenomena — including spontaneous emission, interference with single quanta, cavity quantum electrodynamics, detector discreteness, and mirror behavior — into a single causal architecture, without introducing new field equations or modifying the formalism of Maxwellian electrodynamics or quantum electrodynamics.The speed of light is interpreted as a structural limit governing the maximal rate at which coherent field organization can be maintained across spatial separation, rather than as the velocity of a transported object. The work further identifies a continuity between quantum and gravitational regimes, in which both emerge from a common phase structure but correspond to different domains of realizability.The proposal is structural rather than dynamical in scope. It does not introduce new laws or entities, but specifies where and when physical events are taken to occur within existing electromagnetic theory, thereby providing a unified physical account of emission, interference, reflection, and photon detection.

Гарий Владимирович Ефимов