Robust procedures for converting among Lindblad, Kraus and matrix representations of quantum dynamical semigroups

Abstract

Given an quantum dynamical semigroup expressed as an exponential superoperator acting on a space of N-dimensional density operators, eigenvalue methods are presented by which canonical Kraus and Lindblad operator sum representations can be computed. These methods provide a mathematical basis on which to develop novel algorithms for quantum process tomography, the statistical estimation of superoperators and their generators, from a wide variety of experimental data. Theoretical arguments and numerical simulations are presented which imply that these algorithms will be quite robust in the presence of random errors in the data.Comment: RevTeX4, 31 pages, no figures; v4 adds new introduction and a numerical example illustrating the application of these results to Quantum Process Tomograph