NV-ensemble enabled microwave/NV parametric amplifier with optimal driving

TL;DR

This paper explores optimizing the driving signal in a microwave/NV-center parametric amplifier, finding that a square wave drive enhances amplification performance by approximately 40%.

Contribution

It demonstrates that a multi-harmonic drive, especially a square wave, significantly improves amplifier gain compared to sinusoidal driving.

Findings

Optimal drive is mainly a sum of harmonics of the sum frequency.

Square wave drive increases amplification rate by about 40%.

Limiting to four harmonics improves amplification by about 22%.

Abstract

In our recent study [arXiv:2601.03407] we showed that a hybrid non-degenerate parametric amplifier could be realized for a microwave mode and an ensemble of NV-centers (or other spins) by parametrically driving the spin ensemble. The parametric driving was sinusoidal at the sum of the spin and cavities frequencies. Here we consider whether the performance of the amplifier can be improved by using a more complex drive. Employing numerical optimization, we find that the optimal driving is primarily a sum of harmonics of the sum frequency. The optimal drive, which is essentially a square wave, ramps up the amplification rate by about 40 %, while limiting the drive to four harmonics improves the amplification by about 22 %.