Cloning entangled photons to scales one can see

Pavel Sekatski, Bruno Sanguinetti, Enrico Pomarico, Nicolas Gisin, and Christoph Simon
Phys. Rev. A 82, 053814 – Published 15 November 2010

Abstract

By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with the human eye, potentially bringing quantum effects to macroscopic scales [P. Sekatski, N. Brunner, C. Branciard, N. Gisin, and C. Simon, Phys. Rev. Lett. 103, 113601 (2009)]. In this paper we theoretically study quantum states obtained by amplifying one side of an entangled photon pair with different types of optical cloning machines for photonic qubits. We propose a detection scheme that involves lossy threshold detectors (such as the human eye) on the amplified side and conventional photon detectors on the other side. We show that correlations obtained with such coarse-grained measurements prove the entanglement of the initial photon pair and do not prove the entanglement of the amplified state. We emphasize the importance of the detection loophole in Bell violation experiments by giving a simple preparation technique for separable states that violate a Bell inequality without closing this loophole. Finally, we analyze the genuine entanglement of the amplified states and its robustness to losses before, during, and after amplification.

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  • Received 3 June 2010

DOI:https://doi.org/10.1103/PhysRevA.82.053814

©2010 American Physical Society

Authors & Affiliations

Pavel Sekatski1,*, Bruno Sanguinetti1, Enrico Pomarico1, Nicolas Gisin1, and Christoph Simon2

  • 1Group of Applied Physics, University of Geneva, 20 rue de l’Ecole-de Médecine, CH-1211 Geneva 4, Switzerland
  • 2Institute for Quantum Information Science and Department of Physics and Astronomy, University of Calgary, Calgary T2N 1N4, Alberta, Canada

  • *Pavel.Sekatski@unige.ch

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Vol. 82, Iss. 5 — November 2010

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