Measurement-invisible quantum correlations in scrambling dynamics

TL;DR

This paper investigates measurement-invisible quantum correlations in scrambling dynamics, revealing three distinct phases of correlations and a novel phase transition based on measurement response, advancing understanding of entanglement in complex quantum systems.

Contribution

It introduces a new phase transition within entangled phases characterized by measurement response, providing a novel way to classify entanglement phases.

Findings

Identifies three dynamical phases with distinct quantum correlations.

Discovers a new phase transition based on measurement visibility of correlations.

Shows implications for measurement feedback in quantum information tasks.

Abstract

Scrambling unitary dynamics in a quantum system transmutes local quantum information into a non-local web of correlations which manifests itself in a complex spatio-temporal pattern of entanglement. In such a context, we show there can exist three distinct dynamical phases characterised by qualitatively different forms of quantum correlations between two disjoint subsystems of the system. Transitions between these phases are driven by the relative sizes of the subsystems and the degree scrambling that the dynamics effects. Besides a phase which has no quantum correlations as manifested by vanishing entanglement between the parts and a phase which has non-trivial quantum correlations quantified by a finite entanglement monotone, we reveal a new phase transition within the entangled phase which separates phases wherein the quantum correlations are invisible or visible to measurements on one of the subsystems. This is encoded in the qualitatively different properties of the ensemble of states on one of the subsystems conditioned on the various measurement outcomes on the other subsystem. This provides a new characterisation of entanglement phases in terms of their response to measurements instead of the more ubiquitous measurement-induced entanglement transitions. Our results have implications for the kind of tasks that can be performed using measurement feedback within the framework of quantum interactive dynamics.