Quantum scrambling via accessible tripartite information

Quantum information scrambling (QIS), from the perspective of quantum information theory, is generally understood as local non-retrievability of information evolved through some dynamical process, and is often quantified via entropic quantities such as the tripartite information. We argue that this approach comes with a number of issues, in large part due to its reliance on quantum mutual informations, which do not faithfully quantify correlations directly retrievable via measurements, and in part due to the specific methodology used to compute tripartite informations of the studied dynamics. We show that these issues can be overcome by using accessible mutual informations, defining corresponding 'accessible tripartite informations', and provide explicit examples of dynamics whose scrambling properties are not properly quantified by the standard tripartite information. Our results lay the groundwork for a more profound understanding of what QIS represents, and reveal a number of promising, as of yet unexplored, venues for further research.

Automated summary

Quantum information scrambling (QIS), which is the local non-retrievability of information evolved through dynamic processes, is often quantified using entropic quantities such as the tripartite information. However, this approach has some issues due to its reliance on quantum mutual informations that do not accurately quantify correlations retrievable via measurements, as well as the specific methodology used to compute the tripartite information. By using accessible mutual informations and defining corresponding 'accessible tripartite informations', these issues can be overcome. Our findings lay the groundwork for a deeper understanding of QIS and open up new avenues for further research.