Absence of measurement-induced entanglement transition due to feedback-induced skin effect

TL;DR

This paper demonstrates that feedback-induced skin effects in open quantum systems prevent the measurement-induced entanglement transition, resulting in localized edge states and short-range entanglement, with implications for experimental quantum platforms.

Contribution

It reveals that feedback-induced skin effects suppress entanglement transitions in monitored quantum systems, a phenomenon observable without post selection in experimental setups.

Findings

Feedback-induced skin effect causes particle concentration at edges.

Entanglement transition is suppressed by the skin effect.

Phenomenon is observable in noisy quantum platforms like trapped ions.

Abstract

A quantum many-body system subject to unitary evolution and repeated local measurements with an increasing rate undergoes a measurement-induced entanglement transition from extensive (or subextensive) to area law entropy scaling. We find that certain open boundary systems under "generalized monitoring", consisting of "projective monitoring" and conditional feedback, display an anomalous late-time particle concentration on the edge, reminiscent of the "skin effect" in non-Hermitian systems. Such feedback-induced skin effect will suppress the entanglement generation, rendering the system short-range entangled without measurement-induced entanglement transition. While initially emerged in noninteracting models, such skin effect can also occur in chaotic interacting systems and Floquet quantum circuits subjected to random generalized measurements. Since the dynamics of the skin effect do not require post selection, and can be observed at the particle number level, the phenomenon is experimentally relevant and accessible in noisy intermediate-scale quantum platforms, such as trapped ions.