Structural physical approximations of unphysical maps and generalized quantum measurements
Structural physical approximations of unphysical maps and generalized quantum measurements
We investigate properties of the structural physical approximation (SPA) of the partial transposition map recently introduced by Horodecki and Ekert [Phys. Rev. Lett. 89, 127902 (2002)]. We focus on the case of two-qubit states and show that in this case the map has the structure of a generalized quantum measurement …