Degenerate two-photon Rydberg atom voltage reference

We implement a DC voltage reference by measuring Stark shifts of cesium Rydberg atoms in a vapor cell. Cesium atoms are excited from the ground state to the 15s state via a degenerate two-photon transition that provides a narrow, Doppler free line. The 15s state experiences a scalar, quadratic stark shift which is used to measure the voltage across a parallel plate capacitor integrated into the vapor cell. We demonstrate a sensitivity of