Enhanced quantum sensing with room-temperature solid-state masers

Quantum sensing with solid-state electron spin systems finds broad applications in diverse areas ranging from material and biomedical sciences to fundamental physics. Exploiting collective behavior of noninteracting spins holds the promise of pushing the detection limit to even lower levels, while to date, those levels are scarcely reached because of the broadened linewidth and inefficient readout of solid-state spin ensembles. Here, we experimentally demonstrate that such drawbacks can be overcome by a reborn maser technology at room tem-perature in the solid state. Owing to maser action, we observe a fourfold reduction in the electron paramag-netic resonance linewidth of an inhomogeneously broadened molecular spin ensemble, which is narrower than the same measured from single spins at cryogenic temperatures. The maser-based readout applied to near zero-field magnetometry showcases the measurement signal-to-noise ratio of 133 for single shots. This technique would be an important addition to the toolbox for boosting the sensitivity of solid-state ensemble spin sensors.

Automated summary

Quantum sensing using solid-state electron spin systems is widely applicable in various fields, and the use of reborn maser technology has overcome the drawbacks of broadened linewidth and inefficient readout in solid-state spin ensembles. The maser-based readout has resulted in a fourfold reduction in linewidth and a high signal-to-noise ratio in near zero-field magnetometry.