In this paper, firstly, we discuss the following matrix completion problem in the spectral norm: u x ( i ) ( −π,y )= u x ( i ) ( π,y ), i=0,1,2 . The feasible condition for the above problem is ...

We discuss in particular the case of quantum-state tomography, where the aim is to recover the density matrix, a positive semidefinite matrix, typically normalised with unit trace.

Journal of Computational Mathematics, Vol. 21, No. 2 (MARCH 2003), pp. 175-182 (8 pages) Least-squares solution of AX B = D with respect to symmetric positive semidefinite matrix X is considered. By ...