While work in the past decade has strongly cemented the connection between quantuminformation and quantum gravity, much of the research studies the connection from the
perspective of applying quantum information tools to quantum gravity. In this dissertation,
we aim to study the connection in both directions: not only quantum information for
gravity, but how gravity may offer a window into otherwise intractable problems in quantum
information theory. We begin by exploring the properties of thermal quantum error-correction
codes, derived from the intersection of quantum information and many-body physics, in
AdS/CFT, where the thermodynamic properties of black holes can be more tractable to study
than many-body systems. We then propose a multipartite generalization and prove several
properties of reflected entropy, an entanglement measure derived from studying semiclassical
geometries, where again, the holographic duality of AdS/CFT enables tractable calculations.
Next, we further expand on this program by demonstrating that, under a reasonable set of
assumptions, holographic states saturate a large class of entanglement measures that are often
intractable to compute, such as squashed entanglement. AdS/CFT may therefore provide a
useful arena by which to study various quantum information-theoretic quantities that may
be too complicated to understand in generic quantum systems. We then turn our focus
to generalizing graph-theoretic techniques for studying entanglement in quantum gravity
to quantum information, more broadly. We do this in a systematic fashion, in increasing
order of generality (graphs to hypergraphs to topological knots), showing that they capture
broader swathes of quantum entropies. We complete this line of study with a mathematical
investigation of random tensor networks with non-trivial link states, in which we take a
computational tool common in condensed matter and quantum gravity, and generalize the
tool to capture entanglement properties for a broader class of quantum states.