Broadband and long-duration optical memory in Yb:YSO

TL;DR

This paper demonstrates a broadband, long-duration optical quantum memory in Yb:YSO with high efficiency, optimized optical pumping, and a method for synthesizing complex optical waveforms, advancing quantum network capabilities.

Contribution

It introduces a high-bandwidth, long-storage-time optical memory in Yb:YSO with optimized pumping and waveform synthesis techniques, enabling future quantum network applications.

Findings

250 MHz memory bandwidth achieved

Storage time of up to 125 microseconds

Efficiency of 20% at short times, 5% at 125 microseconds

Abstract

Optical quantum memories are essential components for realizing the full potential of quantum networks. Among these, rare-earth-doped crystal memories stand out due to their large multimode storage capabilities. To maximize the multimode capacity in the time domain, it is key to simultaneously achieve large memory bandwidth and long optical storage time. Here, we demonstrate an atomic frequency comb optical memory in Yb:YSO, with a memory bandwidth of 250 MHz and a storage time of up to 125 $\mu$s. The efficiency reaches 20 % at short storage times, and 5 % at 125 $\mu$s. These results were enabled by an optimized optical pumping scheme, guided by numerical modelling. Our approach is specifically designed for future spin-wave storage experiments, with the theoretical bandwidth limit set at 288 MHz by the hyperfine structure of Yb:YSO. Additionally, we introduce an efficient method for synthesizing the optical pumping waveforms required for generating combs with tens of thousands of teeth, as well as a simple yet frequency-agile laser setup for optical pumping across a 10 GHz bandwidth.