Shot-noise-limited magnetometer with sub-picotesla sensitivity at room temperature

We report a photon shot-noise-limited (SNL) optical magnetometer based on amplitude modulated optical rotation using a room-temperature Rb-85 vapor in a cell with anti-relaxation coating. The instrument achieves a room-temperature sensitivity of 70 fT/root Hz at 7.6 mu T. Experimental scaling of noise with optical power, in agreement with theoretical predictions, confirms the SNL behaviour from 5 mu T to 75 mu T. The combination of best-in-class sensitivity and SNL operation makes the system a promising candidate for application of squeezed light to a state-of-the-art atomic sensor. (C) 2014 AIP Publishing LLC.