Quantum Lyapunov exponent in dissipative systems

The out-of-time order correlator (OTOC) has been widely studied in closed quantum systems. However, there are very few studies for open systems and they are mainly focused on isolating the effects of scrambling from those of decoherence. Adopting a different point of view, we study the interplay between these two processes. This proves crucial in order to explain the OTOC behavior when a phase space contracting dissipation is present, ubiquitous not only in real life quantum devices but in the dynamical systems area. The OTOC decay rate is closely related to the classical Lyapunov exponent-with some differences-and more sensitive in order to distinguish the chaotic from the regular behavior than other measures. On the other hand, it is revealed as a generally simple function of the longest lived eigenvalues of the quantum evolution operator. We find no simple connection with the Ruelle-Pollicott resonances, but by adding Gaussian noise of h over bar eff size to the classical system we recover the OTOC decay rate, which is a consequence of the correspondence principle put forward in Phys. Rev. Lett. 108, 210605 (2012) and Phys. Rev. E 99, 042214 (2019).

Automated summary

This article investigates the out-of-time order correlator (OTOC) in open systems, with a focus on the interplay between the effects of scrambling and decoherence. The study reveals the importance of this interplay in explaining the behavior of OTOC in the presence of phase space contracting dissipation. The OTOC decay rate is found to be related to the classical Lyapunov exponent and serves as a sensitive measure to distinguish chaotic from regular behavior.