High cooperativity coupling of rare earth spins with planar superconducting resonator

TL;DR

This paper demonstrates an ultra-high cooperativity of approximately 650 between rare earth spins and a planar superconducting microwave resonator, advancing integrated hybrid quantum systems for quantum memory and transduction.

Contribution

It reports the first ultra-high cooperativity in a planar superconducting resonator with rare earth spins, using a uniform magnetic field to exploit anisotropic coupling.

Findings

Achieved cooperativity of ~650 between spins and resonator

Demonstrated uniform magnetic field enhances coupling

Paves way for integrated quantum memory and transducers

Abstract

Interfacing superconducting microwave resonator with rare earth doped crystals presents a promising hybrid quantum system for applications including spin-assisted transducers and memories. The coupling strength between spins of rare earth ions and the microwave photons is characterized by the cooperativity. Here we report an ultra-high cooperativity $C \sim$ 650 between rare earth spins and a planar superconducting microwave resonator that features a highly uniform magnetic field for harnessing the strong anisotropic coupling strength of erbium doped yttrium orthosilicate. This cooperativity rivals that from a bulk dielectric resonator and paves a path for efficiently coupling of spins with microwave photons on an integrated platform.