BibTeX Source

@Article{1367-2630-13-6-063031,
  author =       "Enrico Pomarico and Bruno Sanguinetti and Pavel Sekatski and Hugo Zbinden and
                 Nicolas Gisin",
  title =        "Experimental amplification of an entangled photon: what if the detection loophole
                 is ignored?",
  journal =      "New Journal of Physics",
  volume =       "13",
  number =       "6",
  pages =        "063031",
  URL =          "http://stacks.iop.org/1367-2630/13/i=6/a=063031",
  doi =          "10.1088/1367-2630/13/6/063031",
  year =         "2011",
  abstract =     "The experimental verification of quantum features, such as entanglement, at large
                 scales is extremely challenging because of environment-induced decoherence. Indeed,
                 measurement techniques for demonstrating the quantumness of multiparticle systems
                 in the presence of losses are difficult to define, and if they are not sufficiently
                 accurate they can provide wrong conclusions. We present a Bell test where one
                 photon of an entangled pair is amplified and then detected by threshold detectors,
                 whose signals undergo postselection. The amplification is performed by a classical
                 machine, which produces a fully separable micro–macro state. However, by adopting
                 such a technique one can surprisingly observe a violation of the
                 Clauser–Horne–Shimony–Holt inequality. This is due to the fact that ignoring
                 the detection loophole opened by the postselection and the system losses can lead
                 to misinterpretations, such as claiming micro–macro entanglement in a setup where
                 evidently it is not present. By using threshold detectors and postselection, one
                 can only infer the entanglement of the initial pair of photons, and so
                 micro–micro entanglement, as is further confirmed by the violation of a
                 nonseparability criterion for bipartite systems. How to detect photonic
                 micro–macro entanglement in the presence of losses with the currently available
                 technology remains an open question.",
}