Coupling of an erbium spin ensemble to a superconducting resonator

TL;DR

This paper demonstrates a hybrid quantum device coupling erbium spins in a crystal to a superconducting resonator, enabling potential optical-microwave quantum interfaces for future quantum networks.

Contribution

It reports the first realization of a hybrid device with erbium-doped crystal coupled to a superconducting resonator, showing coherent spin coupling.

Findings

Collective spin coupling of 4 MHz observed.

Spin linewidth down to 75 MHz achieved.

Potential for optical-microwave quantum interfaces demonstrated.

Abstract

A quantum coherent interface between optical and microwave photons can be used as a basic building block within a future quantum information network. The interface is envisioned as an ensemble of rare-earth ions coupled to a superconducting resonator, allowing for coherent transfer between optical and microwave photons. Towards this end, we have realized a hybrid device coupling a Er$^{3+}$ doped Y$_2$SiO$_5$ crystal in a superconducting coplanar waveguide cavity. We observe a collective spin coupling of 4 MHz and a spin linewdith of down to 75 MHz.