Measurement-induced multipartite-entanglement regimes in collective spin systems

• URL: http://arxiv.org/abs/2305.10209v4
• Date: Fri, 12 Jan 2024 10:14:59 GMT
• Title: Measurement-induced multipartite-entanglement regimes in collective spin systems
• Authors: Pablo M. Poggi, Manuel H. Mu\~noz-Arias
• Abstract summary: We study the competing effects of collective generalized measurements and interaction-induced scrambling in the dynamics of an ensemble of spin-1/2 particles. We show that the interplay between collective unitary dynamics and measurements leads to three regimes of the average Quantum Fisher Information.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: 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 crossovers 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.

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