Institute for Quantum Information Seminar

Expander graphs play a large role in computer science and information theory, with applications such as derandomizing algorithms and constructing error correcting codes. Recently, a quantum version of these expanders has been developed. I will give an overview of the classical case, and then discuss one application of the quantum case to constructing states of quantum spin chains with the seemingly contradictory properties of large entanglement entropy and small correlations. I will then give a probabilistic construction of quantum expanders, and close with various speculative applications to quantum many-body systems.