Bridging Integrability and Chaos to Decipher Out-of-equilibrium Quantum Matter

ended

The proposal tackles fundamental open questions about out-of-equilibrium quantum matter that have recently become of experimental and technological relevance. The main objectives are: (i) Understand how, and when equilibrium statistical mechanics emerges from the coherent dynamics of closed quantum systems. (ii) Explain the fundamental mathematical structure underlying universal dynamical features. I will address these issues by developing an overarching description of finite-time dynamics based on integrable and chaotic systems. The idea is to characterise quantitatively the dynamics by pinpointing paradigmatic exactly solvable models. The exact solutions of these models will also help to elaborate new analytical and numerical techniques. The proposal encompasses two main parts: WP1-2. WP1 is devoted to integrable systems. These are systems with a macroscopic number of local conservation laws. They play a key role in understanding out-of-equilibrium quantum matter because their dynamics is sufficiently constrained to be, to some extent, solvable. I will devise a general method for describing their large but finite time dynamics. In particular, I will characterise their approach to the asymptotic (generalized) hydrodynamic regime which I recently helped to identify. WP2 focusses on maximally chaotic systems, i.e. systems without local conservation laws. These systems are interesting because are able to model several generic dynamical features. I will characterise the maximally-chaotic dynamics in any spatial dimension using “dual-unitary quantum circuits”, a class of solvable periodically-driven systems that my collaborators and I recently introduced.