Magnetic and optical control in thermal atomic spin ensembles: Principles and applications

This paper provides a comprehensive review of the principles of magnetic and optical control in thermal atomic spin ensembles, as well as recent advances and applications in quantum precision measurement. As a practical macroscopic quantum system, thermal atomic spin ensembles have emerged as a key platform for next-generation quantum sensors due to their exceptional sensitivity, accuracy, and scalability. The review emphasizes how magneto-optical modulation techniques can be employed to extract real-time information about spin dynamics and system states, thereby generating high-quality observables that serve as the foundation for advanced control strategies such as feedback regulation, quantum state estimation, and pulsed manipulation. These techniques are shown to play a crucial role in enhancing measurement sensitivity, dynamic response and long-term stability. In addition, the incorporation of modern control theories, including closed-loop feedback and Kalman filter, has facilitated real-time optimization of atomic spin dynamics, unlocking new levels of sensitivity across a range of applications such as atomic magnetometers, co-magnetometers, inertial sensors, and microwave masers. This paper systematically discusses the synergistic interplay of modulation, measurement, and control in thermal spin ensembles, exploring its potential across a wide range of scientific and engineering applications. These technological advances provide a solid foundation for ultra-sensitive magnetic field detection and show promising prospects in frontier fields such as dark matter detection and gravitational wave observation. Looking ahead, such innovations are expected to further drive the miniaturization and integration of quantum sensors, significantly expanding their utility across disciplines.