# Disentangling Sources of Quantum Entanglement in Quench Dynamics

## TL;DR

This paper investigates the origins of quantum entanglement in fermionic many-body systems after a quench, identifying single-particle contributions, optimizing entanglement bases, and exploring long-term universality and basis transformations to improve quantum simulation methods.

## Contribution

It introduces a method to disentangle single-particle effects from interaction-driven entanglement and finds universal behaviors and basis optimizations in quench dynamics.

## Key findings

- Significant reduction of entanglement using optimized bases.
- Universal entanglement behavior in long-time limits.
- Crossover from real-space to momentum-space entanglement.

## Abstract

Quantum entanglement may have various origins ranging from solely interaction-driven quantum correlations to single-particle effects. Here, we explore the dependence of entanglement on time-dependent single-particle basis transformations in fermionic quantum many-body systems, thus aiming at isolating single-particle sources of entanglement growth in quench dynamics. Using exact diagonalization methods, for paradigmatic non-integrable models we compare to the standard real space cut various physically motivated bipartitions. Moreover, we search for a minimal entanglement basis using local optimization algorithms, which at short to intermediate post-quench times yields a significant reduction of entanglement beyond a dynamical Hartree-Fock solution. In the long-time limit, we identify an asymptotic universality of entanglement for weakly interacting systems, as well as a cross-over from dominant real-space to momentum-space entanglement in Hubbard-models undergoing an interaction quench. Finally, we discuss the relevance of our findings for the development of tensor network based algorithms for quantum dynamics.