Entanglement verification with realistic measurement devices via squashing operations

Tobias Moroder, Otfried Gühne, Normand Beaudry, Marco Piani, and Norbert Lütkenhaus
Phys. Rev. A 81, 052342 – Published 28 May 2010

Abstract

Many protocols and experiments in quantum information science are described in terms of simple measurements on qubits. However in a real implementation the exact description is more difficult and more complicated observables are used. The question arises whether a claim of entanglement in the simplified description still holds, if the difference between the realistic and simplified models is taken into account. We show that a positive entanglement statement remains valid if a certain positive linear map connecting the two descriptions—a so-called squashing operation—exists; then lower bounds on the amount of entanglement are also possible. We apply our results to polarization measurements of photons using only threshold detectors, and derive procedures under which multiphoton events can be neglected.

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  • Received 13 October 2009

DOI:https://doi.org/10.1103/PhysRevA.81.052342

©2010 American Physical Society

Authors & Affiliations

Tobias Moroder1,2,3, Otfried Gühne4,5, Normand Beaudry3, Marco Piani3, and Norbert Lütkenhaus1,2,3

  • 1Quantum Information Theory Group, Institute of Theoretical Physics I, University Erlangen-Nuremberg, Staudtstraße 7/B2, D-91058 Erlangen, Germany
  • 2Max Planck Institute for the Science of Light, Günther-Scharowsky-Straße 1/24, D-91058 Erlangen, Germany
  • 3Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, N2L 3G1 Waterloo, Ontario, Canada
  • 4Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21A, A-6020 Innsbruck, Austria
  • 5Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria

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Issue

Vol. 81, Iss. 5 — May 2010

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