Abstract
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 [1]. 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. We use a rubidium-tuned, polarization-squeezed probe beam to improve the sensitivity of an atomic magnetometer in a proof-of-principle experiment [2]. The magnetometer consists of an optically probed rubidium vapor cell at room temperature and a shot-noise-limited polarimeter. By the Faraday effect, a magnetic field creates a circular birefringence in the vapor. The resulting rotation of the polarization plane of a linearly polarized input beam is seen in the detected signal. The sensitivity of our setup is shot noise limited for a coherent beam input, i.e., any potential signal is measured versus a background noise floor that is the shot noise. To improve the signal-to-noise ratio and hence the sensitivity we employ a polarization-squeezed probe.
© 2011 IEEE
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