Quantum Entanglement in the Sachdev-Ye-Kitaev Model and its Generalizations

TL;DR

This paper reviews recent advances in understanding quantum entanglement in many-body systems using the SYK model and its variants, highlighting entanglement entropy behavior, connections to gravity, and measurement-induced phase transitions.

Contribution

It provides a comprehensive review of entanglement entropy studies in the SYK model, including new insights into its growth, saturation, and effects of measurements, linking quantum information and gravity.

Findings

Entanglement entropy in SYK models shows linear growth and saturation.

Saturation of entanglement relates to replica wormholes in gravity.

Measurement-induced phase transitions occur due to symmetry breaking in replica space.

Abstract

Entanglement is one of the most important concepts in quantum physics. We review recent progress in understanding the quantum entanglement in many-body systems using large-$N$ solvable models: the Sachdev-Ye-Kitaev (SYK) model and its generalizations. We present the study of entanglement entropy in the original SYK Model using three different approaches: the exact diagonalization, the eigenstate thermalization hypothesis, and the path-integral representation. For coupled SYK models, the entanglement entropy shows linear growth and saturation at the thermal value. The saturation is related to replica wormholes in gravity. Finally, we consider the steady-state entanglement entropy of quantum many-body systems under repeated measurements. The traditional symmetry breaking in the enlarged replica space leads to the measurement-induced entanglement phase transition.