  In the long-standing quest to reconcile gravity with quantum mechanics,
profound connections have been unveiled between concepts traditionally
pertaining to quantum information theory, such as entanglement, and
constitutive features of gravity, like holography. Developing and promoting
these connections from the conceptual to the operational level unlocks access
to a powerful set of tools, which can be pivotal towards the formulation of a
consistent theory of quantum gravity. Here, we review recent progress on the
role and applications of quantum informational methods, in particular tensor
networks, for quantum gravity models. We focus on spin network states dual to
finite regions of space, represented as entanglement graphs in the group field
theory approach to quantum gravity, and illustrate how techniques from random
tensor networks can be exploited to investigate their holographic properties.
In particular, spin network states can be interpreted as maps from bulk to
boundary, whose holographic behaviour increases with the inhomogeneity of their
geometric data (up to becoming proper quantum channels). The entanglement
entropy of boundary states, which are obtained by feeding such maps with
suitable bulk states, is then proved to follow a bulk area law, with
corrections due to the entanglement of the bulk state. We further review how
exceeding a certain threshold of bulk entanglement leads to the emergence of a
black hole-like region, revealing intriguing perspectives for quantum
cosmology.
