Workshop on QUANTUM INFORMATION AND FOUNDATIONS OF QUANTUM MECHANICS

Quantum Information Processing and Quantum Communications
On unambiguous state discrimination

aula dottorato  Mercoledì 22 aprile ore 14.00 

DAGMAR
BRUSS, Universitaet Duesseldorf 
>VITAE:
Dagmar Bruss completed her PhD in Heidelberg in elementary particle physics.
Spending two postdoc years in Oxford, she moved into the field of quantum
information
in 1997. After one year at the ISI Torino (as European Research Fellow)
she went to Hannover, where she is currently working in the Theoretical
Quantum Optics group of Maciej Lewenstein. She completed her Habilitation
in 2002. She is now full professor at the Institute fuer Theoretische Physik of the HeinrichHeineUniversitaet Duesseldorf. Her main scientific interests are the theory of entanglement, security issues in quantum cryptography, and quantum optical implementations of quantum information
processing.


Abstract 


Distinguishing two nonorthogonal states in an optimal way is
a fundamental problem in quantum information theory. If one is not
allowed to make an error, this task is called unambiguous state
discrimination (USD). A USD measurement is optimal when it minimises
the probability of an inconclusive outcome. The optimal solution
of USD for two mixed states is not (yet?) analytically known.
We show that the optimal measurement is unique, and present a
general strategy to find the optimal solution. For the
lowestdimensional nontrivial case (i.e. d = 4) our approach
allows to determine the optimal solution in a constructive way,
and to understand the properties of its different regimes. 

