Researchers have demonstrated that the topology of interaction networks between spins significantly influences a quantum system's transition from integrability to chaos and the speed of information propagation. Using a graph-theoretic formulation to model Ising spin networks, it was observed that long-range couplings and heterogeneous degree distributions in the network drastically accelerate quantum information propagation. This finding is crucial for understanding thermalization and non-equilibrium dynamics in many-body quantum systems.
The study employed various diagnostic tools to quantify information scrambling. Out-of-time-order correlators (OTOCs) showed exponential early-time growth, revealing quantum Lyapunov exponents that systematically scale with the parameters of the chaotic regime. Krylov complexity, in turn, indicated rapid operator growth in the chaotic phase, synchronizing with the dynamics of OTOCs and mutual information. Spectrally, the transition manifested as a shift from Poissonian to Wigner-Dyson level spacing statistics, and the spectral form factor (SFF) exhibited the characteristic slope-dip-ramp-plateau structure, allowing the extraction of Thouless and Heisenberg times.
A key result is the correlation between a reduced Thouless time and an acceleration in information and operator scrambling. This suggests that the speed at which a quantum system forgets its initial state and distributes information across all its degrees of freedom is directly linked to the topological properties of its interaction network. The work establishes a unified framework connecting network topology with information-theoretic, operator, and spectral diagnostics, providing a deeper understanding of how the structure of a quantum system affects its dynamic behavior and its path towards thermal equilibrium.