  We analyze the achievable limits of the quantum information processing of the
weak interaction revealed by hyperons with spin. We find that the weak decay
process corresponds to an interferometric device with a fixed visibility and
fixed phase difference for each hyperon. Nature chooses rather low visibilities
expressing a preference to parity conserving or violating processes (except for
the decay $\Sigma^+\longrightarrow p \pi^0$). The decay process can be
considered as an open quantum channel that carries the information of the
hyperon spin to the angular distribution of the momentum of the daughter
particles. We find a simple geometrical information theoretic interpretation of
this process: two quantization axes are chosen spontaneously with probabilities
$\frac{1\pm\alpha}{2}$ where $\alpha$ is proportional to the visibility times
the real part of the phase shift. Differently stated the weak interaction
process corresponds to spin measurements with an imperfect Stern-Gerlach
apparatus. Equipped with this information theoretic insight we show how
entanglement can be measured in these systems and why Bell's nonlocality (in
contradiction to common misconception in literature) cannot be revealed in
hyperon decays. We study also under which circumstances contextuality can be
revealed.
