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Proceedings Paper

Atmospheric turbulence and free-space optical communication using orbital angular momentum of single photons
Author(s): Carl Paterson
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Paper Abstract

The well defined spin and orbital angular momentum states of photons offers a practical realization of quantum digits and a means of secure single-photon optical communication. The orbital angular momentum is associated with the spatial distribution of the wavefunction and the number of orbital angular momentum eigenstates is unlimited, giving the possibility of arbitrary base-N digits. In this paper, free-space optical communications using angular momentum states of single photons is investigated and in particular the effect of atmospheric turbulence on the angular momentum of the photons is modelled. The refractive index fluctuations in the atmosphere perturb the complex amplitude of a propagating beam so that the photons that were launched in an eigenstate of orbital angular momentum are no longer guaranteed to be in the original eigenstate after propagation. By considering the resulting wave as a superposition of angular momentum states, the probability of obtaining correct or incorrect measurements of the transmitted digit is calculated. The effect on a free-space optical communication using orbital angular momentum and the use of adaptive optics is discussed. The information capacity per photon is quantified and compared to that using polarization states for binary digits.

Paper Details

Date Published: 11 November 2004
PDF: 12 pages
Proc. SPIE 5572, Optics in Atmospheric Propagation and Adaptive Systems VII, (11 November 2004); doi: 10.1117/12.565435
Show Author Affiliations
Carl Paterson, Imperial College London (United Kingdom)

Published in SPIE Proceedings Vol. 5572:
Optics in Atmospheric Propagation and Adaptive Systems VII
John D. Gonglewski; Karin Stein, Editor(s)

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