Measurement-induced multipartite-entanglement regimes in collective spin systems

Poggi, Pablo M. and Muñoz-Arias, Manuel H. (2024) Measurement-induced multipartite-entanglement regimes in collective spin systems. Quantum, 8. 1229. ISSN 2521-327X (

[thumbnail of Poggi-Munoz-Arias-Quantum-2023-Measurement-induced-multipartite-entanglement-regimes]
Text. Filename: Poggi-Munoz-Arias-Quantum-2023-Measurement-induced-multipartite-entanglement-regimes.pdf
Final Published Version
License: Creative Commons Attribution 4.0 logo

Download (2MB)| Preview


We study the competing effects of collective generalized measurements and interaction-induced scrambling in the dynamics of an ensemble of spin-1/2 particles at the level of quantum trajectories. This setup can be considered as analogous to the one leading to measurement-induced transitions in quantum circuits. We show that the interplay between collective unitary dynamics and measurements leads to three regimes of the average Quantum Fisher Information (QFI), which is a witness of multipartite entanglement, as a function of the monitoring strength. While both weak and strong measurements lead to extensive QFI density (i.e., individual quantum trajectories yield states displaying Heisenberg scaling), an intermediate regime of classical-like states emerges for all system sizes where the measurement effectively competes with the scrambling dynamics and precludes the development of quantum correlations, leading to sub-Heisenberg-limited states. We characterize these regimes and the transitions between them using numerical and analytical tools, and discuss the connections between our findings, entanglement phases in monitored many-body systems, and the quantum-to-classical transition.