Diagnosing first- and second-order phase transitions with probes of quantum chaos

We explore quantum phase transitions using two probes of quantum chaos: out-of-time-order correlators (OTOCs) and the rparameter obtained from the level spacing statistics. In particular, we address pspin models associated with quantum annealing or reverse annealing. Quantum annealing triggers first-order or second-order phase transitions, which is crucial for the performance of quantum devices. We find that the time-averaging OTOCs for...