Electron spin resonance detected by a superconducting qubit

TL;DR

This paper introduces a novel electron spin resonance detection method using a superconducting qubit as a single-photon detector, enabling highly sensitive measurements of spin ensembles at very low temperatures.

Contribution

The work demonstrates a new hybrid quantum circuit approach for electron-spin resonance spectroscopy with enhanced sensitivity using a superconducting qubit.

Findings

Successful detection of NV center absorption spectrum at 30mK

Measurement of a large spin ensemble (~10^{11} spins)

Enhanced sensitivity in magnetic resonance detection

Abstract

A new method for detecting the magnetic resonance of electronic spins at low temperature is demonstrated. It consists in measuring the signal emitted by the spins with a superconducting qubit that acts as a single-microwave-photon detector, resulting in an enhanced sensitivity. We implement this new type of electron-spin resonance spectroscopy using a hybrid quantum circuit in which a transmon qubit is coupled to a spin ensemble consisting of NV centers in diamond. With this setup we measure the NV center absorption spectrum at 30mK at an excitation level of \thicksim15\,\mu_{B} out of an ensemble of 10^{11} spins.