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Entanglement degradation of a two-mode squeezed vacuum in absorbing and amplifying optical fibers

Abstract

Applying the recently developed formalism of quantum-state transformation of light at absorbing dielectric four-port devices [5], we calculate the quantum state of the outgoing modes of a two-mode squeezed vacuum transmitted through optical fibers of given extinction coefficients. Using the Peres-Horodecki separability criterion for continuous variable systems [4], we then compute both the maximal length of transmission of a two-mode squeezed vacuum through an absorbing system for which the transmitted state is still inseparable and the maximal gain for which inseparability can be observed in an amplifying setup. Finally, we estimate an upper bound of the entanglement preserved after transmission through an absorbing system. The results show that the characteristic length of entanglement degradation drastically decreases with increasing strength of squeezing.

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From Optika i Spektroskopiya, Vol. 91, No. 3, 2001, pp. 441–447.

Original English Text Copyright © 2001 by Scheel, Opatrny, Welsch.

This article was submitted by the authors in English.

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Scheel, S., Opatrny, T. & Welsch, D.G. Entanglement degradation of a two-mode squeezed vacuum in absorbing and amplifying optical fibers. Opt. Spectrosc. 91, 411–417 (2001). https://doi.org/10.1134/1.1405221

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Keywords

  • Quantum State
  • Separable State
  • Wigner Function
  • Gaussian State
  • Entanglement Measure