Coexistence of qubit effects

Autor(en): Busch, Paul
Schmidt, Heinz-Juergen
Stichwörter: CLONING; Coexistence; Effect; Joint measurability; JOINT MEASUREMENTS; Physics; Physics, Mathematical; Physics, Multidisciplinary; Quantum Science & Technology; Qubit; UNCERTAINTY; Unsharp observable
Erscheinungsdatum: 2010
Herausgeber: SPRINGER
Journal: QUANTUM INFORMATION PROCESSING
Volumen: 9
Ausgabe: 2, SI
Startseite: 143
Seitenende: 169
Zusammenfassung: 
Two quantum events, represented by positive operators (effects), are coexistent if they can occur as possible outcomes in a single measurement scheme. Equivalently, the corresponding effects are coexistent if and only if they are contained in the ranges of a single (joint) observable. Here we give several equivalent characterizations of coexistent pairs of qubit effects. We also establish the equivalence between our results and those obtained independently by other authors. Our approach makes explicit use of the Minkowski space geometry inherent in the four-dimensional real vector space of selfadjoint operators in a two-dimensional complex Hilbert space.
ISSN: 15700755
DOI: 10.1007/s11128-009-0109-x

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