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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 5 — Mar. 1, 2010
  • pp: 4499–4509

Witnessing effective entanglement over a 2 km fiber channel

Christoffer Wittmann, Josef Fürst, Carlos Wiechers, Dominique Elser, Hauke Häseler, Norbert Lütkenhaus, and Gerd Leuchs  »View Author Affiliations

Optics Express, Vol. 18, Issue 5, pp. 4499-4509 (2010)

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We present a fiber-based continuous-variable quantum key distribution system. In the scheme, a quantum signal of two non-orthogonal weak optical coherent states is sent through a fiber-based quantum channel. The receiver simultaneously measures conjugate quadratures of the light using two homodyne detectors. From the measured Q-function of the transmitted signal, we estimate the attenuation and the excess noise caused by the channel. The estimated excess noise originating from the channel and the channel attenuation including the quantum efficiency of the detection setup is investigated with respect to the detection of effective entanglement. The local oscillator is considered in the verification. We witness effective entanglement with a channel length of up to 2km.

© 2010 Optical Society of America

OCIS Codes
(270.0270) Quantum optics : Quantum optics
(270.5570) Quantum optics : Quantum detectors
(270.5568) Quantum optics : Quantum cryptography
(270.5585) Quantum optics : Quantum information and processing

ToC Category:
Quantum Optics

Original Manuscript: November 16, 2009
Revised Manuscript: February 1, 2010
Manuscript Accepted: February 2, 2010
Published: February 19, 2010

Christoffer Wittmann, Josef Fürst, Carlos Wiechers, Dominique Elser, Hauke Häseler, Norbert Lütkenhaus, and Gerd Leuchs, "Witnessing effective entanglement over a 2km fiber channel," Opt. Express 18, 4499-4509 (2010)

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