# Single-photon-level light storage in cold atoms using the Autler-Townes splitting protocol

## TL;DR

This paper demonstrates a single-photon-level quantum memory in cold atoms using the Autler-Townes splitting protocol, achieving high efficiency, low noise, and robustness against dephasing, advancing quantum information storage technology.

## Contribution

It is the first experimental realization of a broadband ATS-based quantum memory in ultracold atoms with low noise and high fidelity.

## Key findings

- Stored 20-ns pulses with 0.1 photons on average for 200 ns.
- Achieved 12.5% storage efficiency and signal-to-noise ratio above 30.
- Achieved ultra-low unconditional noise probability of 3.3×10⁻⁴.

## Abstract

Broadband spin-photon interfaces for long-lived storage of photonic quantum states are key elements for quantum information technologies. Yet, reliable operation of such memories in the quantum regime is challenging due to photonic noise arising from technical and/or fundamental limitations in the storage-and-recall processes controlled by strong electromagnetic fields. Here, we experimentally implement a single-photon-level spin-wave memory in a laser-cooled Rubidium gas, based on the recently proposed Autler-Townes splitting (ATS) protocol. We demonstrate storage of 20-ns-long laser pulses, each containing an average of 0.1 photons, for 200 ns with an efficiency of $12.5\%$ and signal-to-noise ratio above 30. Notably, the robustness of ATS spin-wave memory against motional dephasing allows for an all-spatial filtering of the control-field noise, yielding an ultra-low unconditional noise probability of $3.3\times10^{-4}$, without the complexity of spectral filtering. These results highlight that broadband ATS memory in ultracold atoms is a preeminent option for storing quantum light.