Polarization squeezing and continuous-variable polarization entanglement

Natalia Korolkova, Gerd Leuchs, Rodney Loudon, Timothy C. Ralph, and Christine Silberhorn
Phys. Rev. A 65, 052306 – Published 17 April 2002
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Abstract

A concept of polarization entanglement for continuous variables is introduced. For this purpose the Stokes-parameter operators and the associated Poincaré sphere, which describe the quantum-optical polarization properties of light, are defined and their basic properties are reviewed. The general features of the Stokes operators are illustrated by evaluation of their means and variances for a range of simple polarization states. Some of the examples show polarization squeezing, in which the variances of one or more Stokes parameters are smaller than the coherent-state value. The main object of the paper is the application of these concepts to bright squeezed light. It is shown that a light beam formed by interference of two orthogonally polarized quadrature-squeezed beams exhibits squeezing in some of the Stokes parameters. Passage of such a primary polarization-squeezed beam through suitable optical components generates a pair of polarization-entangled light beams with the nature of a two-mode squeezed state. Implementation of these schemes using the double-fiber Sagnac interferometer provides an efficient method for the generation of bright nonclassical polarization states. The important advantage of these nonclassical polarization states for quantum communication is the possibility of experimentally determining all of the relevant conjugate variables of both squeezed and entangled fields using only linear optical elements followed by direct detection.

  • Received 30 May 2001

DOI:https://doi.org/10.1103/PhysRevA.65.052306

©2002 American Physical Society

Authors & Affiliations

Natalia Korolkova1, Gerd Leuchs1, Rodney Loudon1,2, Timothy C. Ralph3, and Christine Silberhorn1

  • 1Lehrstuhl für Optik, Physikalisches Institut, Friedrich-Alexander-Universität, Staudtstrasse 7/B2, D-91058 Erlangen, Germany
  • 2Department of Electronic Systems Engineering, Essex University, Colchester CO4 3SQ, United Kingdom
  • 3Department of Physics, University of Queensland, St. Lucia, Queensland 4072, Australia

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Issue

Vol. 65, Iss. 5 — May 2002

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