Workshop on QUANTUM INFORMATION PROCESSING AND QUANTUM COMMUNICATIONS
Quantum Information Processing and Quantum Communications
How true is fidelity?
|aula 326 - Giovedì 3 giugno ore 11.00|
|RICHARD GILL, Utrecht University|
|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
The analysis will throw new light on the strange convergence rates recently discovered by Bagan, Baig, Munoz-Tapia and Rodriguez (2004; PRA 69, 010304).