Flux qubit as a sensor for a magnetometer with quantum limited sensitivity

TL;DR

This paper proposes using superconducting flux qubits as highly sensitive magnetometers capable of quantum-limited detection, leveraging their low noise and high transfer functions to outperform conventional SQUIDs.

Contribution

It introduces a novel application of flux qubits as magnetometers with near quantum-limited sensitivity, analyzing their transfer functions and noise sources.

Findings

Flux qubits exhibit low noise and high transfer functions.

They can achieve energy resolution close to the Planck constant.

Potential to surpass conventional SQUID magnetometers.

Abstract

We propose to use the quantum properties of a superconducting flux qubit in the construction of a magnetometer with quantum limited sensitivity. The main advantage of a flux qubit is that its noise is rather low, and its transfer functions relative to the measured flux can be made to be about 10mV/$\Phi_0$, which is an order of magnitude more than the best value for a conventional SQUID magnetometer. We analyze here the voltage-to-flux, the phase-to-flux transfer functions and the main noise sources. We show that the experimental characteristics of a flux qubit, obtained in recent experiments, allow the use of a flux qubit as magnetometer with energy resolution close to the Planck constant.