Quantum Wheatstone Bridge

TL;DR

This paper introduces a quantum Wheatstone bridge using a boundary-driven spin chain that leverages quantum interference to enhance sensitivity to unknown couplings, with potential applications in quantum sensing and metrology.

Contribution

It presents the first fully quantum analogue of the Wheatstone bridge, demonstrating enhanced sensitivity via quantum effects and providing a practical framework for implementation.

Findings

Sensitivity peaks at destructive interference points.

Quantum Fisher information quantifies the sensitivity.

Robustness against calibration errors demonstrated.

Abstract

We propose a quantum Wheatstone bridge as a fully quantum analogue to the classical version. The bridge is a few-body boundary-driven spin chain exploiting quantum effects to gain an enhanced sensitivity to an unknown coupling. The sensitivity is explained by a drop in population of an entangled Bell state due to destructive interference as the controllable coupling approaches the unknown coupling. A simple criteria for the destructive interference is found, and an approximate expression for the width of the drop is derived. The sensitivity to the unknown coupling is quantified using the quantum Fisher information, and we show that the state of the bridge can be measured indirectly through the spin current. Our results are robust towards calibration errors and generic in the sense that several of the current state-of-the-art quantum platforms could be used as a means of realization. The quantum Wheatstone bridge may thus find use in fields such as sensing and metrology using near-term quantum devices.