Quantum-enhanced electrometer based on microwave-dressed Rydberg atoms

Rydberg atoms have shown remarkable performance in sensing microwave fields. The sensitivity of such an electrometer based on optical readout of the atomic ensemble has been demonstrated to approach the photon-shot-noise limit. However, the sensitivity cannot be promoted infinitely by increasing the power of the probe light due to the increased collision rates and power broadening. Compared with classical light, the use of quantum light may lead to a better sensitivity with a lower number of photons. In this paper, we exploit entanglement in a microwave-dressed Rydberg electrometer to suppress the fluctuation of noise. The results show a sensitivity enhancement that beats the shot-noise limit in both cold- and hotatom schemes. Through optimizing the transmission of the optical readout, our quantum advantage can be maintained with differing absorptive indexes of the atomic vapor, which makes it possible to apply a quantum light source in the absorptive electrometer.