corner
corner

Phys. Rev. A 80, 042114 (2009) [5 pages]

Concavity of the set of quantum probabilities for any given dimension

Download: PDF (124 kB) Buy this article Export: BibTeX or EndNote (RIS)

Károly F. Pál* and Tamás Vértesi
Institute of Nuclear Research of the Hungarian Academy of Sciences, P.O. Box 51, H-4001 Debrecen, Hungary

Received 19 May 2009; published 30 October 2009

Let us consider the set of all probabilities generated by local binary measurements on two separated quantum systems of a given local dimension d. We address the question of whether the shape of this quantum body is convex or not. We construct a point in the space of probabilities, which is on the convex hull of the local polytope, but still cannot be attained by measuring d-dimensional quantum systems if the number of measurement settings is large enough. From this it follows that this body is not convex. We also show that for finite d the quantum body with the generalized measurement associated with positive operator-valued measures allowed may contain points that cannot be achieved with only projective measurements.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevA.80.042114
DOI:
10.1103/PhysRevA.80.042114
PACS:
03.65.Ta, 03.65.Ud, 03.67.−a

*kfpal@atomki.hu

tvertesi@dtp.atomki.hu