Probing the indistinguishability of single photons generated by Rydberg atomic ensembles

TL;DR

This study assesses the indistinguishability of single photons from Rydberg atomic ensembles using Hong-Ou-Mandel experiments, revealing high indistinguishability for off-resonant excitation and lower values for Rydberg EIT, with implications for quantum networks.

Contribution

It provides the first comparison of photon indistinguishability from Rydberg EIT and off-resonant excitation methods in cold atomic ensembles.

Findings

High indistinguishability (up to 98%) for off-resonant excitation with small detection windows.

Lower indistinguishability values observed for Rydberg EIT-generated photons.

Indistinguishability depends on detection window and excitation method.

Abstract

We investigate the indistinguishability of single photons retrieved from collective Rydberg excitations in cold atomic ensembles. The Rydberg spin waves are created either by off resonant two-photon excitation to the Rydberg state or by Rydberg electromagnetically induced transparency. To assess the indistinguishability of the generated single photons, we perform Hong-Ou-Mandel experiments between the single photons and weak coherent states of light. We analyze the indistinguishability of the single photons as a function of the detection window and for photons generated by off-resonant excitation we infer high value of indistinguishability going from 89% for the full waveform to 98% for small detection windows. In the same way, we also investigate for the first time the indistinguishability of single photons generated by Rydberg EIT, showing values lower than those corresponding to single photons generated by off-resonant excitation. These results are relevant for the use of Rydberg atoms as quantum network nodes.