Quantum Sensing of Intermittent Stochastic Signals

TL;DR

This paper explores how the number of quantum sensors and their fidelity influence sensitivity to continuous and intermittent signals, highlighting the importance of near-perfect fidelity for detecting stochastic, intermittent signals.

Contribution

It demonstrates the scaling laws for sensor number and fidelity needed for optimal sensitivity, especially emphasizing the role of quantum projection noise near eigenstates.

Findings

Increasing sensor number by 1/F^2 recovers sensitivity for continuous signals.

More sensors are required for intermittent signals to match single perfect sensor performance.

Near-unity fidelity and quantum projection noise limit are crucial for sensing stochastic signals.

Abstract

Realistic quantum sensors face a trade-off between the number of sensors measured in parallel and the control and readout fidelity ($F$) across the ensemble. We investigate how the number of sensors and fidelity affect sensitivity to continuous and intermittent signals. For continuous signals, we find that increasing the number of sensors by $1/F^2$ for $F<1$ always recovers the sensitivity achieved when $F=1$. However, when the signal is intermittent, more sensors are needed to recover the sensitivity achievable with one perfect quantum sensor. We also demonstrate the importance of near-unity control fidelity and readout at the quantum projection noise limit by estimating the frequency components of a stochastic, intermittent signal with a single trapped ion sensor. Quantum sensing has historically focused on large ensembles of sensors operated far from the standard quantum limit. The results presented in this manuscript show that this is insufficient for quantum sensing of intermittent signals and re-emphasizes the importance of the unique scaling of quantum projection noise near an eigenstate.