Four Wave Mixing from Fe3+ Spins in Sapphire

TL;DR

This paper reports the first observation of four wave mixing in Fe3+ doped sapphire resonators, demonstrating a new nonlinear microwave interaction enabled by electron spins at cryogenic temperatures, with potential quantum applications.

Contribution

It introduces the first demonstration of four wave mixing from Fe3+ spins in sapphire, revealing a third-order nonlinear susceptibility at microwave frequencies.

Findings

First observation of FWM in Fe3+ sapphire resonators

Identification of a third-order paramagnetic nonlinearity

Potential for quantum measurement and control applications

Abstract

Fe3+ ions in sapphire exhibit an Electron Spin Resonance (ESR) which interacts strongly with high-Q Whispering Gallery (WG) modes at microwave frequencies. We report the first observation of a third-order paramagnetic nonlinear susceptibility in such a resonator at cryogenic temperatures, and the first demonstration of four wave mixing (FWM) using this parametric nonlinearity. This observation of an all-microwave nonlinearity is an enabling step towards a host of quantum measurement and control applications which utilize spins in solids.