Off-Axis Magnetic Sensing via Dissipative Spin Dynamics Probed by Time-Resolved Fluorescence in Diamond.

Magnetic field sensing with a nitrogen-vacancy (NV) center in diamond typically relies on coherent spin manipulation, which is susceptible to spin dephasing noise. Here, we demonstrate an alternative protocol that exploits dissipative spin dynamics, probed through time-resolved fluorescence, to extract off-axis magnetic field information without relying on spin coherence. The approach operates under continuous optical excitation and leverages spin-dependent transition channels to encode both the strength and orientation of the magnetic field into the fluorescence dynamics. Numerical simulations incorporating Gaussian magnetic noise confirm that the protocol remains robust against spin dephasing, maintaining a stable estimation performance even under short coherence times. We further develop a general parameter estimation framework based on photoluminescence trajectories, enabling off-axis field reconstruction from experimental measurements. The method is experimentally validated and may be adapted to other fluorescence-based spin defect platforms including silicon carbide and hexagonal boron nitride.