4 papers
Optimal covariant quantum measurements
Erkka Haapasalo, Juha-Pekka Pellonpää
We discuss symmetric quantum measurements and the associated covariant observables modelled, respectively, as instruments and positive-operator-valued measures. The emphasis of thi…
The Choi-Jamiolkowski isomorphism and covariant quantum channels
Erkka Haapasalo
A generalization of the Choi-Jamiolkowski isomorphism for completely positive maps between operator algebras is introduced. Particular emphasis is placed on the case of normal unit…
Compatibility of covariant quantum channels with emphasis on Weyl symmetry
Erkka Haapasalo
Compatibility conditions of quantum channels featuring symmetry through covariance are studied. Compatibility here means the possibility of obtaining two or more channels through p…
Effective methods for constructing extreme quantum observables
Erkka Haapasalo, Juha-Pekka Pellonpaa
We study extreme points of the set of finite-outcome positive-operator-valued measures (POVMs) on finite-dimensional Hilbert spaces and particularly the possible ranks of the effec…