Covertness as a resource constraint in quantum target sensing

Abstract:Quantum covert target sensing aims to detect low-reflectivity targets embedded in the thermal environment while avoiding discovery by an adversary. This covertness requirement constrains the admissible probe energy, thereby imposing a trade-off between covertness and sensing performance. However, how this resource constraint determines the ultimate estimation precision of the target parameter remains largely unexplored. To fill this gap, we establish a unified framework connecting covert target discrimination with quantum-enhanced parameter estimation. We first present perturbative $\epsilon$-covertness-induced bounds on the probe energy, which yield an admissible energy window narrowing as $\mathcal{O}(\sqrt{\epsilon/M})$. Moreover, we introduce the covertness-constrained quantum Fisher information (CCQFI) to quantify the ultimate precision of target-reflectivity estimation and assess its attainability with specific measurements. For Gaussian-distributed coherent-state (GCS) and two-mode squeezed vacuum (TMSV) probes, their CCQFIs scale as $\mathcal{O}(\epsilon)$ and $\mathcal{O}(M)+\mathcal{O}(\sqrt{\epsilon M})+\mathcal{O}(\epsilon)$, respectively. In particular, in the strong covertness regime $\epsilon\to0$, the GCS CCQFI vanishes, whereas the TMSV retains a finite $\mathcal{O}(M)$ contribution exhibiting a pronounced metrological advantage. Besides, photon counting saturates the GCS CCQFI, whereas homodyne detection achieves a higher attainability for the TMSV probe. Our work identifies covertness as a quantitative resource constraint governing the metrological limits of quantum target sensing.

arXiv:2610.03233 [quant-ph]

(or arXiv:2610.03233v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.03233 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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