title: Fidelity decay as an efficient indicator of quantum chaos.
abstract: We demonstrate that a system's rate of fidelity decay under repeated perturbations may be measured efficiently on a quantum information processor, and analyze the conditions under which this indicator is a reliable probe of quantum chaos. The type and rate of the decay are not dependent on the eigenvalue statistics of the unperturbed system, but depend on the system's eigenvector statistics in the eigenbasis of the perturbation. For random eigenvector statistics, the decay is exponential with a rate fixed by the variance of the perturbation's energy spectrum. Hence, even classically regular models can exhibit an exponential fidelity decay under generic quantum perturbations. These results clarify which perturbations can distinguish classically regular and chaotic quantum systems.
authors.affiliation: Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Emerson
authors.forename: Yaakov S
authors.initials: YS
authors.lastname: Weinstein
authors.forename: Seth
authors.initials: S
authors.lastname: Lloyd
authors.forename: D G
authors.initials: DG
authors.lastname: Cory