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Conference on Lasers and Electro-Optics

Quantum Noise Limited and Entanglement-Assisted Magnetometry

Kasper Jensen, Wojciech Wasilewski, Hanna Krauter, Jelmer J. Renema, M. V. Balabas, Eugene Simon Polzik

Published Jan 1, 2010• 18 citations
Publisher

Abstract

We demonstrate a radio frequency atomic magnetometer with sub-femtoTesla/ Hz sensitivity, mainly limited by projection noise of atoms. Furthermore, we demonstrate that Einstein-Podolsky-Rosen entanglement of atoms enhances the sensitivity to broadband magnetic fields.
DOI
10.1364/qels.2010.qthn6

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The ability to measure magnetic fields with high sensitivity is a key requirement in many physical, biological and medical applications. Currently the most sensitive magnetometers are optical magnetometers, in which the polarization of an atomic sample responds to the field and is read out by an optical measurement. These instruments are limited by two fundamental sources of quantum noise: projection noise of the atoms and shot noise of the light. For magnetometers designed to have a high statistical sensitivity, contributions from both sources are comparable. Here we show that the sensitivity can be improved by the application of non-classical light.
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We propose and demonstrate a radio-frequency (rf) atomic magnetometer based on parametric resonances. Previously, most rf atomic magnetometers are based on magnetic resonances and their sensitivities are often limited by spin-exchange relaxation. Here, we introduce a novel scheme for an rf magnetometer where the rf magnetic field is measured by exciting the parametric resonances instead of magnetic resonances using parametric modulation fields. In this way, the spin-exchange relaxation is almost eliminated. Benefiting from the low spin relaxation rate, the parametric resonance scheme exhibits a narrower linewidth and stronger signal, which results in a higher sensitivity. With a 6×6×3 mm^{3} Rb atomic vapor cell, we developed an rf atomic magnetometer with a noise floor of 2 fT/Hz^{1/2}, which is about one order of magnitude higher than the sensitivity achieved in the magnetic-resonance-based scheme. The presented rf detection scheme holds promise in advancing rf atomic magnetometers and brings new insight into their various applications.