Optimal quantum transport on a ring via locally monitored chiral quantum walks

TL;DR

This paper presents a method to enhance quantum transport on a ring by combining chiral quantum walks with local monitoring, avoiding fine-tuning and lifting dark states through spectral analysis.

Contribution

It introduces a novel framework that integrates chirality and local measurements to optimize quantum transfer efficiency without precise timing.

Findings

Chirality breaks time-reversal symmetry, aiding dark state suppression.

Local monitoring improves detection probability without fine-tuning.

Spectral analysis of the Perron-Frobenius operator guides optimal conditions.

Abstract

In purely coherent transport on finite networks, destructive interference can significantly suppress transfer probabilities, which can only reach high values through careful fine-tuning of the evolution time or tailored initial-state preparations. We address this issue by investigating excitation transfer on a ring, modeling it as a locally monitored continuous-time chiral quantum walk. Chirality, introduced through time-reversal symmetry breaking, imparts a directional bias to the coherent dynamics and can lift dark states. Local monitoring, implemented via stroboscopic projective measurements at the target site, provides a practical detection protocol without requiring fine-tuning of the evolution time. By analyzing the interplay between chirality and measurement frequency, we identify optimal conditions for maximizing the asymptotic detection probability. The optimization of this transfer protocol relies on the spectral properties of the Perron-Frobenius operator, which capture the asymptotic non-unitary dynamics, and on the analysis of dark states. Our approach offers a general framework for enhancing quantum transport in monitored systems.