Single-shot magnetic-field gradiometry from spin-spin correlations in quantum sensor arrays

Coherent control and individual readout of spin systems have expanded the toolbox for quantum sensing and imaging of classical fields. Quantum sensors based on coherent spin precession rely on phase accumulation of long-lived superpositions of states in either single spins or ensembles of spins to estimate the parameters of classical fields with high sensitivity and spatial resolution. We demonstrate a sensing platform that combines site-resolved, single-shot readout with common-mode rejection and gradient estimation. Our platform is based on two-dimensional arrays of individual rubidium atoms held within optical tweezers and engineered linear magnetic-field gradients. We report single-shot, multi-parameter estimation of the global phase and a linear magnetic-field gradient from spin-spin correlations and spatial Fourier modes of individual images; the magnetic-field gradient can be estimated from spatial correlations over interrogation times exceeding the decay time of the shot-averaged Ramsey contrast. We report the noise-equivalent gradient sensitivity and quantify stability and precision using two-clock measurement protocols. Our results establish correlation-based atom-array gradiometry as a powerful tool for single-shot, common-mode-rejected quantum sensing and microscale spatial imaging of magnetic fields.