Magnet field sensing beyond the standard quantum limit under the effect of decoherence

TL;DR

This paper investigates how entangled quantum sensors can surpass the standard quantum limit under realistic decoherence, especially non-Markovian noise, by optimizing exposure time.

Contribution

It demonstrates that entangled sensors can outperform classical limits despite decoherence when the exposure time is carefully optimized in non-Markovian environments.

Findings

Entangled sensors can beat the standard quantum limit with proper exposure time.

Non-Markovian effects allow for improved sensor performance.

Independent dephasing is a common noise source in quantum systems.

Abstract

Entangled states can potentially be used to outperform the standard quantum limit which every classical sensor is bounded by. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior sensor to classical technology via a quantum strategy which is subject to the effect of realistic noise. This paper presents an investigation of how a quantum sensor composed of many spins is affected by independent dephasing. We adopt general noise models including non-Markovian effects, and in these noise models the performance of the sensor depends crucially on the exposure time of the sensor to the field. We have found that, by choosing an appropriate exposure time within non-Markovian time region, an entangled sensor does actually beat the standard quantum limit. Since independent dephasing is one of the most typical sources of noise in many systems, our results suggest a practical and scalable approach to beating the standard quantum limit.