Ergodicity broken in quantum systems even after long evolution

Researchers have re-examined existing concepts and developed a framework for understanding a persistent memory effect in quantum systems that challenges the classical definition of ergodicity. The work demonstrates that a permanent signature of a system’s initial state and early evolution causes nonergodic behavior even after infinite time. This birthmark framework reveals a ubiquitous memory effect arising from universal and revival enhancements, and the stadium billiard is used as a concrete example to identify quantum birthmarks. The team’s findings open an unexplored avenue for understanding the elusive quantum nature of ergodicity, extending scarring theories to more general systems. Quantum systems, unlike their classical counterparts, retain a persistent memory of their initial conditions, even after extended periods of evolution. This challenges the classical definition of ergodicity, which posits complete loss of memory as a system uniformly explores available phase space. The team’s analysis reveals a fundamental quantum bound, demonstrating that quantum dynamics cannot achieve fully statistical, ergodic behavior. Anton M. Graf of Harvard University and colleagues propose an extension of scarring theories to account for both short- and long-term dynamical events that remain unforgotten within quantum systems. This isn’t simply about unusual states; the research indicates ergodicity breaking is an extension of…