Nonexistence of entangled continuous-variable Werner states with positive partial transpose
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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.
McNulty , D , Tatham , R & Mista , L 2014 , ' Nonexistence of entangled continuous-variable Werner states with positive partial transpose ' , Physical Review. A, Atomic, molecular, and optical physics , vol. 89 , no. 3 , 032315 . https://doi.org/10.1103/PhysRevA.89.032315
Physical Review. A, Atomic, molecular, and optical physics
DescriptionD.M. acknowledges the support of the Operational Program Education for Competitiveness Project No. CZ.1.07/2.3.00/20.0060 co-financed by the European Social Fund and Czech Ministry of Education. L.M. would like to acknowledge the Project No. P205/12/0694 of GAČR.
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