Exceptional points and quantum correlations in precise measurements

TL;DR

This paper explores how exceptional points in a monitored two-level quantum system influence quantum correlations and passage times, revealing that measurement precision near these points significantly alters entanglement and non-classical correlations.

Contribution

It introduces a non-Hermitian effective Hamiltonian approach to analyze quantum correlations and passage times in precisely measured two-level systems near exceptional points.

Findings

Quantum correlations decrease in the monitored system near exceptional points.

Passage time becomes half of the measurement duration at exceptional points.

Geometric methods can better reveal the transfer of quantum correlations.

Abstract

We examine the physical manifestations of exceptional points and passage times in a two-level system which is subjected to quantum measurements and which admits a non-Hermitian description. Using an effective Hamiltonian acting in the two-dimensional space spanned by the evolving initial and final states, the effects of highly precise quantum measurements in which the monitoring device interferes significantly with the evolution dynamics of the monitored two-level system is analysed. The dynamics of a multipartite system consisting of the two-level system, a source of external potential and the measurement device is examined using correlation measures such as entanglement and non-classical quantum correlations. Results show that the quantum correlations between the monitored (monitoring) systems is considerably decreased (increased) as the measurement precision nears the exceptional point, at which the passage time is half of the measurement duration. The results indicate that the underlying mechanism by which the non-classical correlations of quantum systems are transferred from one subsystem to another may be better revealed via use of geometric approaches.