Increasing decoherence rate of Rydberg polaritons due to accumulating dark Rydberg atoms

TL;DR

This paper experimentally investigates how dark Rydberg states, which accumulate over time, increase the decoherence rate of Rydberg polaritons in a weak-interaction regime, revealing an additional decoherence mechanism.

Contribution

It introduces a theoretical model including decay to dark states and DDI effects, explaining the observed decoherence increase in Rydberg polaritons.

Findings

Dark Rydberg states contribute to increased decoherence.

Experimental data aligns with the extended theoretical model.

Decay from bright to dark states was quantitatively measured.

Abstract

We experimentally observed an accumulative type of nonlinear attenuation and distortion of slow light, i.e., Rydberg polaritons, with the Rydberg state $|32D_{5/2}\rangle$ in the weak-interaction regime. The present effect of attenuation and distortion cannot be explained by considering only the dipole-dipole interaction (DDI) between Rydberg atoms in $|32D_{5/2}\rangle$. Our observation can be attributed to the atoms in the dark Rydberg states other than those in the bright Rydberg state, i.e., $|32D_{5/2}\rangle$, driven by the coupling field. The dark Rydberg states are all the possible states, in which the population decaying from $|32D_{5/2}\rangle$ accumulated over time, and they were not driven by the coupling field. Consequently, the DDI between the dark and bright Rydberg atoms increased the decoherence rate of the Rydberg polaritons. We performed three different experiments to verify the above hypothesis, to confirm the existence of the dark Rydberg states, and to measure the decay rate from the bright to dark Rydberg states. In the theoretical model, we included the decay process from the bright to dark Rydberg states and the DDI effect induced by both the bright and dark Rydberg atoms. All the experimental data of slow light taken at various probe Rabi frequencies were in good agreement with the theoretical predictions based on the model. This study pointed out an additional decoherence rate in the Rydberg-EIT effect, and provides a better understanding of the Rydberg-polariton system.