Alok Aggarwal, Leonidas J. Guibas, et al.
Discrete and Computational Geometry
An even stronger effect that bound entangled states can have is presented; states which are conjectured to be undistillable become distillable by adding positive partial transpose (PPT) bound entanglement. These conjectured bound entangled states are referred to as negative partial transpose (NPT) bound entangled states.
Alok Aggarwal, Leonidas J. Guibas, et al.
Discrete and Computational Geometry
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Physical Review A - AMO
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Nature
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Journal of High Energy Physics