Parts | Days | Selection | Search | Updates | Downloads | Help
THU: Thursday Contributed Sessions
THU 7: Entanglement and Complexity: Contributed Session to Symposium II
THU 7.7: Talk
Thursday, September 11, 2025, 15:45–16:00, ZHG008
Complexity transitions in chaotic quantum systems — •Gopal Chandra Santra1,2,3, Alex Windey1,2, Soumik Bandyopadhyay1,2, Andrea Legramandi1,2, and Philipp Hauke1,2 — 1Pitaevskii BEC Center, INO-CNR and Department of Physics, University of Trento, Via Sommarive 14, I-38123 Trento, Italy — 2INFN-TIFPA, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento, Italy — 3Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
Complex quantum systems---composed of many interacting particles---are intrinsically hard to model. In the presence of disorder, such systems transition into non-ergodic and localized regimes, reducing relevant basis states. Whether these transitions also reflect abrupt complexity changes remains open. We study such transition in the power-law random banded matrix, Rosenzweig-Porter, and hybrid SYK+Ising models, comparing three complexity markers: fractal dimension, entanglement entropy, and stabilizer Rényi entropy. All markers show sharp transitions between high- and low-complexity phases, though at distinct critical points. Thus, while markers align in ergodic and localized regimes, they diverge in an intermediate fractal phase. The stabilizer Rényi entropy is sensitive to many-body symmetries such as fermion parity and time reversal. Our findings show different markers capture complementary facets of complexity, requiring their combination for a comprehensive diagnosis of phase transitions and revealing implications for classical simulability of chaotic systems.
Keywords: ergodicity transitions; random matrix models; Sachdev-Ye-Kitaev model; entanglement; nonstabilizerness