Closed-Loop Control of ³He Nuclear Spin Oscillator: Implementation via Metastability Exchange Optical Pumping (MEOP)

Achieving long spin coherence times is crucial for quantum precision measurements, and closedloop control techniques are often employed to accomplish this goal. Here, we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a MEOP-based polarized ³He system. We analyze the effects of feedback theoretically and validate our predictions experimentally. With optimized feedback parameters, the spin coherence time T₂ is extended by an order of magnitude. When the feedback strength surpasses a critical threshold, robust maser oscillations are spontaneously excited, demonstrating remarkable resistance to environmental noise and maintaining stable oscillation. This proof-of-principle experiment highlights the viability of MEOP-based ³He spin oscillators, especially in low-frequency domains. The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast, high-precision magnetic field measurements.