00804nas a2200145   4500000000100000008004100001100002100042700002200063700002200085245006000107856004500167300000700212490000600219520043300225       2018                            d1 aŁukasz Rudnicki1 aZbigniew Puchała1 aKarol Życzkowski00aGauge invariant information concerning quantum channels  uhttps://doi.org/10.22331/q-2018-04-11-60  a600 v23 a<p>Motivated by the gate set tomography we study quantum channels from the perspective of information which is invariant with respect to the gauge realized through similarity of matrices representing channel superoperators. We thus use the complex spectrum of the superoperator to provide necessary conditions relevant for complete positivity of qubit channels and to express various metrics such as average gate fidelity.</p>