Towards broadband, high dynamic-range diamond maser amplifiers

Masers were the original quantum-limited microwave amplifier [1], but the bulkiness of traditional travelling-wave masers and the costly cryogenics limited adoption except in applications with exceptionally exacting noise requirements. Recently, renewed interest in quantum-limited amplifiers prompted by the demands of quantum information processing (QIP) and dark matter searches has coincided with the discovery that nitrogen-vacancy centres in diamond can serve as an especially efficient maser gain medium [2-5]. This suggests a route to diamond masers as compact quantum amplifiers for QIP and dark matter searches, but thus far diamond masers have operated in resonant cavities with an inherent gain–bandwidth trade-off.

Here we discuss how strategies used to evolve resonant Josephson parametric amplifiers into broadband travelling-wave parametric amplifiers (TWPAs) [6] can be applied to diamond masers to develop broadband, quantum-limited diamond maser amplifiers. Such broadband masers may have advantages over TWPAs for high dynamic range due to the high input saturation powers typically observed in masers.

[1] C. M. Caves, Phys. Rev. D 26, 1817 (1982)

[2] J. D. Breeze et al., Nature 555, 493–496 (2018)

[3] D. M. Arroo et al., Appl. Phys. Lett. 119, 140502 (2021)

[4] T. Day et al., Phys. Rev. X 14, 041066 (2024)

[5] M. Ohta et al., arXiv:2505.05705 (2025)

[6] M. Esposito et al., Appl. Phys. Lett. 119, 120501 (2021)