Positive partial transpose from spectra
Résumé
In this paper we solve the following problem. Let Hnm be a Hilbert space of dimension nm, and let A be a positive semidefinite self-adjoint linear operator on Hnm. Under which conditions on the spectrum has A a positive partial transpose (is PPT) with respect to any partition Hn⊗Hm of the space Hnm as a tensor product of an n-dimensional and an m-dimensional Hilbert space? We show that the necessary and sufficient conditions can be expressed as a set of linear matrix inequalities (LMIs) on the eigenvalues of A.