Projection Spin Noise in Optical Quantum Sensors Based on Thermal Atoms
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IC AND MOLECULAR PHYSICS
Projection Spin Noise in Optical Quantum Sensors Based on Thermal Atoms A. K. Vershovskiia,*, S. P. Dmitrieva, G. G. Kozlovb, A. S. Pazgaleva, and M. V. Petrenkoa a Ioffe
b Spin
Institute, St. Petersburg, Russia Optics Laboratory, St. Petersburg State University, St. Petersburg, Russia *e-mail: [email protected]
Received December 27, 2019; revised March 10, 2020; accepted March 10, 2020
Abstract—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. DOI: 10.1134/S1063784220080204
INTRODUCTION Thanks to the introduction of compact laser sources of narrow-band optical radiation, the last decade has been characterized by a rapid growth of interest in optical quantum sensors, i.e., devices that use optical control of the state of an ensemble of atoms by methods of electron paramagnetic resonance (EPR) and optical detection of this state. Despite the emergence of numerous new schemes using laser cooling of atoms, quantum sensors that work on ensembles of thermal atoms are increasingly being developed and are being used more widely. The shorter lifetime of the atomic states in these schemes is compensated by their simplicity, compactness, and most importantly by a significantly larger number of atoms being probed. These devices include magnetometers [1] and frequency standards [2] that use EPR transitions in the Zeeman or hyperfine structure of the ground state of alkaline atoms, magnetometers on the transitions in the metastable state of helium-4 [3], and gyroscopes that use, in addition to EPR, nuclear magnetic resonance (NMR) in inert gases, and, in fact, are a combination of EPR and NMR magnetometers, the connection between which is carried out by means of spinexchange interaction between electronic and nuclear paramagnets [4, 5]. It is known [1] that the most fundamental limitation on the sensitivity of quantum sensors is determined by the number of atoms being probed and their relaxation time. A statistical noise, which is due to the
finiteness of the number of atoms and the possible values of their moment projections, is called “spin” or “atomic” quantum projection noise [6]. The study of this noise is of independent int
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