Improving Rabi Attenuation: Toward a Quantum-Based Microwave Attenuation Standard with Atomic Vapor

Quantum sensing of microwave power has attracted increasing attention due to its various potential advantages. Recently we have demonstrated a quantum-based microwave attenuation measurement based on Rabi frequency, i.e., Rabi attenuation, using a cesium atomic vapor cell inserted in a rectangular waveguide. This paper reports on the optimization of the Rabi frequency measurement to improve the accuracy and dynamic range of the Rabi attenuation. As the first step in the optimization process, we reduced microwave detuning by carefully determining the resonant frequency. We also improved the method to determine the Rabi frequency. Consequently, we found that the Rabi attenuation corresponding to the change in power of the microwave signal generator was two orders less uncertain and one order more linear than in the previous study. These results pave the way for realizing a next-generation quantum-based attenuation standard with greater accuracy and broader dynamic range by further improving the Rabi attenuation.