Accessible nonlinear entanglement witnesses

Juan Miguel Arrazola, Oleg Gittsovich, and Norbert Lütkenhaus
Phys. Rev. A 85, 062327 – Published 28 June 2012

Abstract

Verification of entanglement is an important tool to characterize sources and devices for use in quantum computing and communication applications. In a vast majority of experiments entanglement witnesses (EWs) are used in order to prove the presence of entanglement in a quantum state. EWs can be constructed from available measurement results and do not require a reconstruction of the whole density matrix (full tomography), which is especially valuable for high-dimensional systems. We provide a method to construct accessible nonlinear EWs, which incorporate two important properties. First, they improve on linear EWs in the sense that each nonlinear EW detects more entangled states than its linear counterpart and therefore allows the verification of entanglement without critical dependence on having found the “right” linear witness. Second, they can be evaluated using exactly the same data as for the evaluation of the original linear witness. This allows a reanalysis of published experimental data to strengthen statements about entanglement verification without the requirement to perform additional measurements. These particular properties make the accessible nonlinear EWs attractive for the implementations in current experiments, for they can also enhance the statistical significance of the entanglement verification.

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  • Received 18 March 2012

DOI:https://doi.org/10.1103/PhysRevA.85.062327

©2012 American Physical Society

Authors & Affiliations

Juan Miguel Arrazola, Oleg Gittsovich, and Norbert Lütkenhaus

  • Institute for Quantum Computing, University of Waterloo, 200 University Avenue West, N2L 3G1 Waterloo, Ontario, Canada
  • Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, N2L 3G1 Waterloo, Ontario, Canada

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Issue

Vol. 85, Iss. 6 — June 2012

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