Parameter trajectory engineering for state transfer and quantum sensing in non-Hermitian two-level systems

TL;DR

This paper explores how designing parameter trajectories in non-Hermitian two-level systems influences state transfer robustness and quantum sensing capabilities, revealing topological effects and enabling enhanced sensor performance.

Contribution

It introduces a framework linking trajectory topology to system dynamics, demonstrating how to engineer robust state transfer and high-sensitivity quantum sensors.

Findings

Trajectories avoiding EP support robust symmetric transfer.

Encircling EP yields chiral transfer governed by topological winding.

Eigenstate-based sensing achieves full parameter selectivity.

Abstract

Exceptional points (EPs) in non-Hermitian systems give rise to enhanced sensitivity and chiral state transfer, which are important for quantum technologies. Although parameter trajectories encircling EPs can control symmetric and chiral state transfer, their robustness against practical perturbations and their role in quantum sensing remain largely unexplored. Here, we study three time-modulated parameter loops in a non-Hermitian two-level system to show how trajectory design governs state-transfer symmetry, robustness, and sensing performance. Trajectories avoiding the EP support robust symmetric transfer, while those encircling the EP yield chiral transfer governed by the topological winding number, whose robustness depends on the distance to the EP and the encircling direction. For quantum sensing, trajectory engineering enables tuning of sensitivity amplitude, time window, and parameter selectivity in both eigenvalue-based and eigenstate-based sensors. Notably, eigenstate-based sensing achieves full parameter selectivity that is unattainable with eigenvalue-based methods. Our results establish a quantitative connection between trajectory topology and system dynamics, providing a unified framework for robust state-transfer protocols and high-performance quantum sensors.