Photon polarization

Résumé

Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. An individual photon can be described as having right or left circular polarization, or a superposition of the two. Equivalently, a photon can be described as having horizontal or vertical linear polarization, or a superposition of the two. The description of photon polarization contains many of the physical concepts and much of the mathematical machinery of more involved quantum descriptions, such as the quantum mechanics of an electron in a potential well. Polarization is an example of a qubit degree of freedom, which forms a fundamental basis for an understanding of more complicated quantum phenomena. Much of the mathematical machinery of quantum mechanics, such as state vectors, probability amplitudes, unitary operators, and Hermitian operators, emerge naturally from the classical Maxwell's equations in the description. The quantum polarization state vector f

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https://en.wikipedia.org/wiki/Photon_polarization

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Polarization of photons emitted by decaying dark matter

Anna Tokareva

Radiatively decaying dark matter may be searched through investigating the photon spectrum of galaxies and galaxy clusters. We explore whether the properties of dark matter can be constrained through the study of a polarization state of emitted photons. Starting from the basic principles of quantum mechanics we show that the models of symmetric dark matter are indiscernible by the photon polarization. However, we find that the asymmetric dark matter consisted of Dirac fermions is a source of circularly polarized photons, calling for the experimental determination of the photon state. (C) 2016 The Authors. Published by Elsevier B.V.

Elsevier2017

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Polarization Characterization of Soft X-Ray Radiation at FERMI FEL-2

Eugenio Ferrari, David Gauthier

The control of polarization state in soft and hard X- ray light is of crucial interest to probe structural and symmetry properties of matter. Thanks to their Apple-II type undulators, the FERMI-Free Electron Lasers are able to provide elliptical, circular or linearly polarized light within the extreme ultraviolet and soft X- ray range. In this paper, we report the characterization of the polarization state of FERMI FEL-2 down to 5 nm. The results show a high degree of polarization of the FEL pulses, typically above 95%. The campaign of measurements was performed at the Low Density Matter beamline using an electron Time-Of-Flight based polarimeter.

Mdpi Ag2017

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Photons traveling cosmological distances through the inhomogeneous Universe experience a great variation in their in-medium induced effective mass. Using the EAGLE suite of hydrodynamical simulations, we infer the free electron distribution and thereby the effective photon mass after reionization. We use this data to study the inter-conversion of kinetically mixed photons and dark photons, which may occur at a great number of resonance redshifts, and obtain the "optical depth" against conversion along random lines-of-sight. Using COBE/FIRAS, Planck, and SPT measurements, we constrain the dark photon parameter space from the depletion of CMB photons into dark photons that causes both spectral distortions and additional anisotropies in the CMB. Finally, we also consider the conversion of sub-eV dark radiation into ordinary photons. We make the line-of-sight distributions of both, free electrons and dark matter, publicly available.

IOP PUBLISHING LTD2020

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