  Using measures of entanglement such as negativity and tangles we provide a
detailed analysis of entanglement structures in pure states of non-interacting
qubits. The motivation for this exercise primarily comes from holographic
considerations, where entanglement is inextricably linked with the emergence of
geometry. We use the qubit systems as toy models to probe the internal
structure, and introduce some useful measures involving entanglement negativity
to quantify general features of entanglement. In particular, our analysis
focuses on various constraints on the pattern of entanglement which are known
to be satisfied by holographic sates, such as the saturation of Araki-Lieb
inequality (in certain circumstances), and the monogamy of mutual information.
We argue that even systems as simple as few non-interacting qubits can be
useful laboratories to explore how the emergence of the bulk geometry may be
related to quantum information principles.
