Localization properties in disordered quantum many-body dynamics under continuous measurement

TL;DR

This paper investigates how disorder and continuous measurement influence localization and dynamical properties in quantum many-body systems, revealing distinct effects on fidelity decay and proposing a practical measurement scheme.

Contribution

It introduces a novel analysis of measurement-induced phase transitions using quantum trajectories and presents a method to measure physical quantities without postselection.

Findings

Disorder and measurement lead to different dynamical behaviors despite both suppressing entanglement.

Fidelity shows anomalous power-law decay in large-disorder, weak-measurement regimes.

Proposed measurement scheme reduces experimental costs significantly.

Abstract

We study localization properties of continuously monitored dynamics and associated measurement-induced phase transitions in disordered quantum many-body systems on the basis of the quantum trajectory approach. By calculating the fidelity between random quantum trajectories, we demonstrate that the disorder and the measurement can lead to dynamical properties distinct from each other, although both have a power to suppress the entanglement spreading. In particular, in the large-disorder regime with weak measurement, we elucidate that the fidelity exhibits an anomalous power-law decay before saturating to the steady-state value. Furthermore, we propose a general method to access physical quantities for quantum trajectories in continuously monitored dynamics without resorting to postselection. It is demonstrated that this scheme drastically reduces the cost of experiments. Our results can be tested in ultracold atoms subject to continuous measurement and open the avenue to study dynamical properties of localization, which cannot be understood from the stationary properties of the entanglement entropy.