I have a target unitary that I want to implement and I have a known dynamics that results in a quantum channel. I already have some fidelity measures to characterize the overlap between them. (like: https://arxiv.org/abs/0909.0077) But I want a more straightforward method to see their difference.
What I have in mind is something like separating the quantum channel into two parts. One is the 'unitary' part that only involves rotation of the state vector. The other is decoherence which causes the Bloch vector to 'shrink'. It sounds like finding two sets of Kraus operators. Is there a way to do this and compare the 'unitary' part of the quantum channel with the target unitary?