Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Matrices of fidelities for ensembles of quantum states and the Holevo
  quantity   The entropy of the Gram matrix of a joint purification of an ensemble of K
mixed states yields an upper bound for the Holevo information Chi of the
ensemble. In this work we combine geometrical and probabilistic aspects of the
ensemble in order to obtain useful bounds for Chi. This is done by constructing
various correlation matrices involving fidelities between every pair of states
from the ensemble. For K=3 quantum states we design a matrix of root fidelities
that is positive and the entropy of which is conjectured to upper bound Chi.
Slightly weaker bounds are established for arbitrary ensembles. Finally, we
investigate correlation matrices involving multi-state fidelities in relation
to the Holevo quantity.

30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph