Information scrambling at finite temperature in local quantum systems
Subhayan Sahu, Brian Swingle
Abstract
Quantum information scrambling provides diagnostics about how information spreads when an isolated quantum system evolves in time. Here, the authors study the temperature dependence of scrambling in locally gapped systems. Using tensor networks, they numerically evaluate out-of-time-ordered commutators in a large, strongly interacting spin chain as a function of temperature. They find that scrambling crucially depends on the ordering of operators around the thermal circle, exposing subtleties in information propagation at finite temperature. For a regulated operator ordering, the butterfly velocity decreases with lowering the temperature, as seen in the figure. The low temperature behavior is derived from a field-theoretical analysis.