John Bollinger, NIST Time and Frequency Div., Boulder, CO

I will discuss how trapped-ion crystals can be used to simulate models of quantum magnetism and describe in more detail experiments with single-plane crystals of hundreds of trapped ions.  Benchmarking quantum dynamics is a challenge as the number of trapped ions grows.  To benchmark quantum dynamics, we measure the evolution of spin-squeezing and so-called out-of-time-order correlations (OTOCs).  OTOCs quantify the build-up of correlations and the spread of quantum information, and are accessible through global spin measurements and time reversal of the engineered dynamics.