Moritz Ernst: Optimizing Input-Output Fidelities

Moritz Ernst, IQC

Abstract

The optimization of quantum information theoretical quantities is a
very difficult problem. As a toy model we investigate the input-output
fidelities of Pauli channels (unital qubit channels). The averaged
fidelity shows nontrivial behaviour. We propose an algorithm to
optimize the fidelity. We find, for some Pauli channels, nontrivial
local maxima, whose fidelities also show nontrivial behaviour.
Finally, we generalize our algorithm to non-unital Pauli channels and
prove that our algorithm will find local maxima.