Miniaturising the NV^- Diamond Maser, Towards Faster and Quantum-Noise Limited Amplification of Qubit Readout at Room Temperature

Masers, the microwave analogue of the laser, can amplify the weakest microwave signals which would allow them to revolutionize medical diagnostics and mobile communications. Previous studies explored them as low noise amplifiers in sensing and cryogen-free noise reduction through absorbing thermal photons. However, to this day continuous-wave masers are still trapped in specialist laboratories due to requiring large electromagnets, cryogenic cooling, and vacuum chambers.<br/><br/>We present the first room-temperature continuous-wave maser that can be transported easily out of the laboratory and onto the benchtop. The device uses an NV^- diamond gain medium that has been manufactured with isotopic purity to achieve significantly longer coherence times that allow it to sustain masing under more compact and less uniform magnet systems. We then provide further avenues towards miniaturisation through developing methods to reduce the magnetic field requirements of the gain material with angular orientation. Finally, new developments towards lower frequency masing with diamond, to match common frequencies used by 5G telecommunications and transmon qubit readout, will be discussed.<br/><br/>This lays the foundations for reducing the footprint of the magnet systems in the future, as well as spurs the search for new materials that could mase at different microwave frequencies, thus widening the applicable bandwidth of ultra-sensitive sensing which masers can provide. This opens opportunities for other research groups and industries to use its exquisite low-noise capabilities in mobile communication and the growing quantum computing field, which relies on faint microwave signals for qubit readout.