Quantum-enhanced NMR Co-Magnetometers Based on Encounter-propagating Pump Beams

Nuclear Magnetic Resonance (NMR) co-magnetometers are advanced quantum sensors capable of measuring angular velocity for inertial navigation. Within the Rb-Xe atomic ensemble, Rb atoms absorb polarized light, decreasing electron spin polarization as the light travels greater distances. This attenuation causes a gradient in Rb spin polarization that severely affects atomic relaxation characteristics and degrades NMR sensors’ performance. Considering atomic diffusion motion, a theoretical simulation model is developed and the spatial distribution of electron spin polarization under the encounter-propagating dual-beam configuration is simulated. The simulation results demonstrate that the proposed dual-beam scheme achieves a more uniform distribution of electron polarization within the atomic vapor cell. Experiments reveal an 18% enhancement in ¹²⁹Xe nuclear spin polarization using the dual-beam scheme compared to the conventional single-beam. Through the Fermi contact interaction between optically pumped Rb and Xe atoms, a more uniform spatial distribution of Rb spin polarization reduces the gradient relaxation of Xe atoms and its depolarization effects, thereby significantly enhancing the macroscopic Xe spin polarization and the signal-to-noise ratio (SNR) of NMR sensors. This study presents a new method for improving atomic polarization, significantly enhancing the performance of quantum sensors.