Multiparameter estimation with solid-state quantum sensors

We demonstrate multiparameter estimation using a solid-state quantum sensor based on a nitrogen–vacancy (NV) center in diamond. By leveraging electronic–nuclear spin entanglement and optimized Bell-state readout, we simultaneously estimate the amplitude, detuning, and phase of a microwave field from a single measurement sequence, achieving linear sensitivity scaling for all parameters under realistic, room-temperature conditions. Furthermore, we introduce a quantum-control protocol that resolves singularities in the quantum Fisher information matrix, enabling simultaneous amplitude and frequency estimation with optimal linear and quadratic scalings. These results establish a practical route toward entanglement- and control-assisted multiparameter quantum sensing with solid-state platforms.