0603168v1

related topics
{states, state, optimal}
{group, space, representation}
{let, theorem, proof}
{measurement, state, measurements}
{information, entropy, channel}
{key, protocol, security}
{error, code, errors}
{observables, space, algebra}

Extremal covariant measurements

G. Chiribella, G. M. D'Ariano

abstract: We characterize the extremal points of the convex set of quantum measurements that are covariant under a finite-dimensional projective representation of a compact group, with action of the group on the measurement probability space which is generally non-transitive. In this case the POVM density is made of multiple orbits of positive operators, and, in the case of extremal measurements, we provide a bound for the number of orbits and for the rank of POVM elements. Two relevant applications are considered, concerning state discrimination with mutually unbiased bases and the maximization of the mutual information.

oai_identifier:
oai:arXiv.org:quant-ph/0603168
categories:
quant-ph
comments:
11 pages, no figures
doi:
10.1063/1.2349481
arxiv_id:
quant-ph/0603168
journal_ref:
J. Math. Phys. 47, 092107 (2006)
created:
2006-03-20

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