A near-quantum-limited diamond maser amplifier operating at millikelvin temperatures

TL;DR

This paper demonstrates a diamond-based maser amplifier operating at millikelvin temperatures with ultra-low noise, high gain, and practical power handling, advancing microwave quantum technology applications.

Contribution

It introduces a near-quantum-limited diamond maser amplifier functioning at millikelvin temperatures, showcasing its potential for quantum microwave signal amplification.

Findings

Power gain exceeding 30 dB

Minimum noise temperature of 0.86 K

Maximum output compression point of -63 dBm

Abstract

Microwave quantum technologies require amplification of weak signals with minimal added noise at millikelvin temperatures. This stringent demand has been met with superconducting parametric amplifiers. While masers offer another fundamental approach, their dependence on cryogenic operation has historically posed challenges for classical communication technologies -- a barrier that does not apply to microwave quantum technologies. In this work, we demonstrate an ultra-low-noise maser amplifier utilizing impurity spins in diamond at millikelvin temperatures. We achieve power gains exceeding $\mathrm{30\,dB}$, a minimum noise temperature of $\mathrm{0.86\,K}$ (corresponding to $2.2$ noise photons), and a maximum $\mathrm{1\,\text{dB}}$ output compression point of $\mathrm{-63\,dBm}$ at $\mathrm{6.595\,\text{GHz}}$. Our results establish masers as viable components of microwave quantum technologies.