Perhaps the most remarkable application of the concept of holographic entanglement entropy has been in the field of black hole entropy studies.
In 2014 Engelhardt and Wall introduced the concept of QES=Quantum Extremal Surfaces that are used in the definition of GSL=Generalized Second Law of blackhole thermodynamics.
Why should the QES proposal be right? Hints to this question are provided by tensor network toy models and a close relationship between QES proposal and quantum error correction.