  The understanding of open quantum systems is crucial for the development of
quantum technologies. Of particular relevance is the characterisation of
divisible quantum dynamics, seen as a generalisation of Markovian processes to
the quantum setting. Here, we propose a way to detect divisibility and quantify
how non-divisible a quantum channel is through the concept of channel
discrimination. We ask how well we can distinguish generic dynamics from
divisible dynamics. We show that this question can be answered efficiently
through semidefinite programming, which provides us with an operational and
efficient way to quantify divisibility.
