Confusability graphs for symmetric sets of quantum states

Giulio Chiribella, Yuxiang Yang

Published 2013-01-07, updated 2013-01-10Version 2

For a set of quantum states generated by the action of a group, we consider the graph obtained by considering two group elements adjacent whenever the corresponding states are non-orthogonal. We analyze the structure of the connected components of the graph and show two applications to the optimal estimation of an unknown group action and to the search for decoherence free subspaces of quantum channels with symmetry.