Nonexistence of entangled continuous-variable Werner states with positive partial transpose

Daniel McNulty*, Richard Tatham, Ladislav Mista

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
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Abstract

We address an open question about the existence of entangled continuous- variable (CV) Werner states with positive partial transpose (PPT). We prove that no such state exists by showing that all PPT CV Werner states are separable. The separability follows by observing that these CV Werner states can be approximated by truncating the states into a finite-dimensional convex mixture of product states. In addition, the constituents of the product states comprise a generalized non-Gaussian measurement which gives, rather surprisingly, a strictly tighter upper bound on quantum discord than photon counting. These results uncover the presence of only negative partial transpose entanglement and illustrate the complexity of more general nonclassical correlations in this paradigmatic class of genuine non-Gaussian quantum states.

Original languageEnglish
Article number032315
Number of pages8
JournalPhysical Review. A, Atomic, molecular, and optical physics
Volume89
Issue number3
DOIs
Publication statusPublished - 12 Mar 2014

Keywords

  • Separability criterion
  • Quantum nonlocality
  • Discord

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