Calibration of spin-light coupling by coherently induced Faraday rotation

Calibrating the strength of light-matter interaction is an important experimental task in quantum information and state engineering protocols. The off-resonant multi-atom spin oscillators can be characterized by readout rate Γ S . Here we introduce method named Coherently Induced FAraday Rotation (CIFAR) for determining rate. suited both continuous pulsed oscillator, relying only on applying a known polarization modulation to probe laser beam detecting optical component. Importantly, does not require changes magnetic fields performing preparation probing. CIFAR signal also independent photo-detection efficiency, allows direct extraction other parameters interaction, such as tensor coupling ζ , damping γ We verify this wave regime, probing strongly coupled oscillator prepared warm cesium atomic vapour.