Quantum electrodynamics and light rays

E. C. G. Sudarshan

Light is a quantum electrodynamic entity and hence bundles of rays must be describable in this framework. We demonstrate the duality in the description of elementary optical phenomena in terms of two-point correlation functions and in terms of collections of light rays. The generalizations necessary to deal with two-slit interference and diffraction by a rectangular slit are worked out and the usefulness of the notion of rays of darkness is illustrated. Quantum electrodynamics, to which Julian Schwinger has so definitively contributed1), is the theory of light at the present state of our knowledge. It has provided models of other field theories, particularly of weak interactions. Despite this the quantum electrodynamic description of light has not been satisfactorily developed. One recalls that Max Planck, the pioneer of quantum theory made a systematic study of light rays and radiative transfer 2) in which quantum concepts did not enter in any significant way. The general theory of quantum optics has so far ignored the question of the connection between light rays and quantum electrodynamics with the notable exception of the recent work of Wolf3). Unlike the notion of light rays in the short wavelength

R. J. Rivers

Clara Valeria Fuchs, Thomas Filk A

It is argued that from a formal point of view, the classical limit of light quanta or photons is not that of a point-like particle but that of a geometric ray. According to this view, standard particle-wave dualism, which is often used in schools to describe the quantum behavior of massive objects, could be replaced by a ray-wave dualism (or even a particle-ray-wave trialism), which seems to be more appropriate for massless quantum objects such as photons. We compare the limits leading from quantum electrodynamics to a classical (Hamiltonian) theory of particles for electrons with those leading from photons via Maxwell’s equations to geometric ray optics. We also discuss the question to which extent Maxwell’s theory for electromagnetic waves should be considered as being on the same formal level as Schrödinger’s or Dirac’s theory.

Andrey Nikolaevich Volobuev, Eugene S. Petrov, Eugene L. Ovchinnikov

The light propagation through system a polarizer-analyzer is investigated on the basis of quantum conceptions about the nature of light. It is shown, that Malus law based on principles of classical electrodynamics not completely takes into account all effects which can occur at the light propagation through system a polarizer-analyzer. The phenomenon of possible change of frequency of light in particular drops out, for example in the region of X-ray radiation. The deduction of Malus law based on quantum principles is given. For comparison the differential effective section of interaction of a photon and electron with take into account of rotation of a plane of polarization of a photon in Compton’s effect is found.

Alessandro Bettini