00817nas a2200157   4500000000100000000000100001008004100002100002100043700002200064700002200086245006000108856004500168300000700213490000600220520043300226       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>