Hybrid non-degenerate parametric amplifier for a microwave cavity mode and an NV ensemble

TL;DR

This paper presents a novel hybrid non-degenerate parametric amplifier combining a microwave cavity and an NV spin ensemble, capable of amplifying signals and generating squeezing at room and cryogenic temperatures with practical experimental considerations.

Contribution

It introduces a new hybrid parametric amplification scheme using a modulated spin ensemble coupled to a cavity, enabling amplification and squeezing without requiring the spin ensemble to be directly resonant.

Findings

Achieves approximately 18 dB amplification with typical cavity parameters.

Generates about 5 dB of squeezing at cryogenic temperatures.

Operates effectively at room and cryogenic temperatures with feasible experimental setups.

Abstract

We introduce an implementation of a non-degenerate parametric amplifier in which the signal and idler modes, respectively, a microwave mode and an ensemble of spins (e.g., nitrogen-vacancy centers in diamond), are operated in their linear regime. This paramp, which amplifies signals in both parts at room and cryogenic temperatures, can be used to generate both the two-mode and single-mode squeezing of either system. It requires merely modulating the frequency of the spin ensemble at the sum of the cavity and spin frequencies (providing the classical pump) with the two systems sufficiently detuned. This effect is remarkable given that modulating a spin ensemble by itself produces neither amplification nor squeezing, unlike modulating an oscillator, and that an off-resonant perturbative analysis would suggest that modulating the spin ensemble merely parametrically drives the cavity mode. With typical cavity parameters including a cavity quality factor~$Q=10^4$, and a 1 GHz modulation amplitude, the microwave signal can be amplified by approximately $18~\mbox{dB}$ in $1.7~\mbox{$\mu$s}$, with a resonant bandwidth of about $0.5~\mbox{MHz}$. At $10~\mbox{mK}$ with the same modulation amplitude and a cavity and spin $Q=5\times 10^4$ it generates approximately $5~\mbox{dB}$ of squeezing. We also examine the experimental requirements for implementation.