2025/10/15 by Xiang, Tai, Lu, Yue-Hui, Ho, Jacquelyn +3
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.2510.13150
Ladder-type two-photon excitation of an atom from a ground state |g⟩, to an intermediate excited state |e⟩, and, finally, to a Rydberg state |r⟩, has a variety of uses from quantum information to sensing. A common scheme for detecting this transition optically is through electromagnetically induced transparency (EIT). However, in inverted wavelength schemes, where the ground-to-excited transition wavelength is shorter than the excited-to-Rydberg transition wavelength, the strength of the EIT feature on the lower-leg beam is strongly reduced in a Doppler-broadened medium. Here, we report on an alternative two-photon spectroscopic feature, which we term the two-photon Autler-Townes resonance, observed on the upper-leg beam. Compared to the EIT signal, this feature's superior signal-to-noise ratio allows one to resolve Rydberg resonances with principal quantum number as high as n=80. We also show that such a feature can be utilized to generate an error signal for stabilizing the frequency of the upper-leg beam.