Universal bound on the Lyapunov spectrum of quantum master equations

TL;DR

This paper establishes a universal bound on the decay rates of quantum master equations using Lyapunov exponents, linking quantum spectral properties with dynamical systems theory.

Contribution

It provides a new proof of a universal bound on decay rates of quantum master equations, connecting spectral properties of positive maps with Lyapunov exponents.

Findings

Derived a bound on decay rates depending only on system dimension

Explicitly determined the dimension-dependent prefactor

Linked quantum spectral analysis with dynamical systems concepts

Abstract

The spectral properties of positive maps are pivotal for understanding the dynamics of quantum systems interacting with their environment. Furthermore, central problems in quantum information such as the characterization of entanglement can be reformulated in terms of spectral properties of positive maps. The present work aims to contribute to a better understanding of the spectrum of positive maps. Specifically, our main result is a new proof of a universal bound on the $d^{2}-1$ generically non vanishing decay rates $\Gamma_{i}$ of time-autonomous quantum master equations on a $d$-dimensional Hilbert space: $$\Gamma_{\mathrm{max}}\,\leq\,\varkappa_{d}\,\sum_{i=1}^{d^{2}-1}\Gamma_{i}$$ The prefactor $\varkappa_{d}$ %, which we explicitly determine, depends only on the dimension $d$ and varies depending on the sub-class of positive maps to which the semigroup solution of the master equation belongs. We provide a brief but self-consistent survey of these concepts. We obtain our main result by resorting to the theory of Lyapunov exponents, a central concept in the study of dynamical systems, control theory, and out-of-equilibrium statistical mechanics. We thus show that progress in understanding positive maps in quantum mechanics may require ideas at the crossroads between different disciplines. For this reason, we adopt a notation and presentation style aimed at reaching readers with diverse backgrounds.