When nature entangles millions of particles: from quantum materials to black holes

Complex many-particle quantum entanglement is a central theme in two distinct major topics in physics: the strange metal state found in numerous correlated electron compounds, and the quantum theory of black holes in Einstein gravity. The Sachdev-Ye-Kitaev model provides a solvable theory of entangled many-particle quantum states without quasiparticle excitations. I will describe how this toy model has led to realistic universal models of strange metals, and to new insights on the quantum states of black holes.