Quantum Information Processing and Quantum Communications

How true is fidelity?

aula 326 - Giovedì 3 giugno ore 11.00
  RICHARD GILL, Utrecht University

Richard Gill (born 1951) is Professor in Mathematical Statistics at the University of Utrecht, Netherlands. He is a member of the Dutch Academy of Sciences. In recent years he has been working on the statistical approach to quantum state reconstruction problems, and on statistical aspects of Bell-type experiments.

Richard Gill
  I will explain a statistical approach to quantum tomography (quantum state reconstruction; also reconstruction of quantum operations) using the tools of Fisher information and maximum likelihood estimation. Applications will be sketched to the issue of adaptive versus non-adaptive, joint versus separate measurement schemes, and (in state tomography) use of entangled versus non-entangled probe states. I will argue that already in the most simple quantum tomography problem (separate measurements on many copies of a two-level system) there is so much rich structure, that a single number figure of merit (such as average fidelity with respect to a "noninformative" prior) does not reflect the complexity of the problem.
The analysis will throw new light on the strange convergence rates recently discovered by Bagan, Baig, Munoz-Tapia and Rodriguez (2004; PRA 69, 010304).