Projection spin noise in optical quantum sensors based on thermal atoms

The principal limitations imposed by spin (or atomic) quantum projection noise on the sensitivity of optical quantum sensors on thermal atoms, which include frequency standards, magnetometers, and gyroscopes that use optical detection of electron paramagnetic resonance, have been theoretically and experimentally studied. The effect of increasing the rms amplitude of the projection noise in a magnetometric scheme under the influence of a strong optical pumping has been demonstrated. Its explanation has been proposed and experimentally confirmed: it has been shown that this effect is explained by the invariance of the integral power of projection noise in relation to the magnetic resonance linewidth in a wide range of pumping intensities An experimental study of the parameters of projection noise in a magnetometric quantum sensor has been conducted and recommendations for optimizing the sensor parameters have been given.