Quantum sensing of intermittent stochastic signals

An ideal quantum sensor would comprise a large ensemble of $M$ quantum systems with uniform high fidelity control and readout ($F$), but experimental demonstrations face a trade-off between $M$ and $F$. We investigate how the number of sensors and fidelity affect sensitivity for a range of signals. We consider estimation of the variance and frequency of stochastic signals. For continuous signals we find that increasing the number of sensors by $1/F^2$ for $F<1$ recovers the sensitivity achievable when $F=1$. However, there is a stronger dependence on $F$ when the signal is intermittent. We demonstrate this with a single trapped ion sensor to highlight the importance of high fidelity control and reaching the quantum projection noise limit.