Bell-inequality violation with entangled photons, free of the coincidence-time loophole

Jan-Åke Larsson, Marissa Giustina, Johannes Kofler, Bernhard Wittmann, Rupert Ursin, and Sven Ramelow
Phys. Rev. A 90, 032107 – Published 16 September 2014

Abstract

In a local realist model, physical properties are defined prior to and independent of measurement and no physical influence can propagate faster than the speed of light. Proper experimental violation of a Bell inequality would show that the world cannot be described with such a model. Experiments intended to demonstrate a violation usually require additional assumptions that make them vulnerable to a number of “loopholes.” In both pulsed and continuously pumped photonic experiments, an experimenter needs to identify which detected photons belong to the same pair, giving rise to the coincidence-time loophole. Here, via two different methods, we derive Clauser-Horne- and Eberhard-type inequalities that are not only free of the fair-sampling assumption (thus not being vulnerable to the detection loophole), but also free of the fair-coincidence assumption (thus not being vulnerable to the coincidence-time loophole). Both approaches can be used for pulsed as well as for continuously pumped experiments. Moreover, as they can also be applied to already existing experimental data, we finally show that a recent experiment [Giustina et al., Nature (London) 497, 227 (2013)] violated local realism without requiring the fair-coincidence assumption.

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  • Received 26 March 2014

DOI:https://doi.org/10.1103/PhysRevA.90.032107

©2014 American Physical Society

Authors & Affiliations

Jan-Åke Larsson1,*, Marissa Giustina2, Johannes Kofler3, Bernhard Wittmann2, Rupert Ursin2, and Sven Ramelow2,4,5,†

  • 1Institutionen för Systemteknik, Linköpings Universitet, 581 83, Linköping, Sweden
  • 2Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090, Vienna, Austria
  • 3Max Planck Institute of Quantum Optics (MPQ), Hans-Kopfermannstraße 1, 85748, Garching/Munich, Germany
  • 4Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090, Vienna, Austria
  • 5Cornell University, 271 Clark Hall, 142 Science Dr., Ithaca, 14853, New York, USA

  • *jan-ake.larsson@liu.se
  • sven.ramelow@univie.ac.at

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Issue

Vol. 90, Iss. 3 — September 2014

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