High Bandwidth Atomic Magnetometery with Continuous Quantum Non-demolition Measurements

TL;DR

This paper reports an experimental advancement in atomic magnetometry, achieving higher bandwidth and sensitivity through continuous quantum non-demolition measurements, with potential for sub-fT sensitivity using spin-squeezed atomic vapor.

Contribution

Demonstrated a four-fold increase in measurement bandwidth in a high sensitivity alkali-metal magnetometer using continuous QND measurements.

Findings

Achieved 22 fT/Hz^{1/2} magnetic field sensitivity

Expanded bandwidth to 1.9 kHz

Operated with only 1% spin polarization

Abstract

We describe an experimental study of spin-projection noise in a high sensitivity alkali-metal magnetometer. We demonstrate a four-fold improvement in the measurement bandwidth of the magnetometer using continuous quantum non-demolition (QND) measurements. Operating in the scalar mode with a measurement volume of 2 cm^3 we achieve magnetic field sensitivity of 22 fT/Hz^(1/2) and a bandwidth of 1.9 kHz with a spin polarization of only 1%. Our experimental arrangement is naturally back-action evading and can be used to realize sub-fT sensitivity with a highly polarized spin-squeezed atomic vapor.