Phase-sensitive quantum spectroscopy with high-frequency resolution

Classical sensors for spectrum analysis are widely used but lack micro- or nanoscale spatial resolution. On the other hand, quantum sensors, capable of working with nanoscale precision, do not provide precise frequency resolution over a wide range of frequencies. Using a single spin in diamond, we present a measurement protocol for quantum probes which enables full signal reconstruction on a nanoscale spatial resolution up to potentially 100 GHz. We achieve 58 nT /√{Hz } amplitude and 0.095 rad /√{Hz } phase sensitivity and a relative frequency uncertainty of 10⁻¹² for a 1.51 GHz signal within 10 s of integration. This technique opens the way to quantum spectrum analysis methods with potential applications in electron spin detection and nanocircuitry in quantum technologies.