  One way to diagnose chaos in bipartite unitary channels is via the tripartite
information of the corresponding Choi state, which for certain choices of the
subsystems reduces to the negative conditional mutual information (CMI). We
study this quantity from a quantum information-theoretic perspective to clarify
its role in diagnosing scrambling. When the CMI is zero, we find that the
channel has a special normal form consisting of local channels between
individual inputs and outputs. However, we find that arbitrarily low CMI does
not imply arbitrary proximity to a channel of this form, although it does imply
a type of approximate recoverability of one of the inputs. When the CMI is
maximal, we find that the residual channel from an individual input to an
individual output is completely depolarizing when the other input is maximally
mixed. However, we again find that this result is not robust. We also extend
some of these results to the multipartite case and to the case of Haar-random
pure input states. Finally, we look at the relationship between tripartite
information and its Renyi-2 version which is directly related to
out-of-time-order correlation functions. In particular, we demonstrate an
arbitrarily large gap between the two quantities.
