Efficient Pumping of Spectral Holes in a Tm$^{3+}$: YAG Crystal for Broadband Quantum Optical Storage

Abstract: Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Here, we report a storage efficiency greater than 28% in a Tm$^{3+}$: YAG crystal in elevated temperatures and without compromising the memory bandwidth. Using various pumping and optimization techniques, we demonstrate multi-frequency window storage with a high memory bandwidth of 630 MHz. Moreover, we propose a general method for large-bandwidth atomic-frequency memory with non-Kramers rare-earth-ion (REI) in solids enabling significantly higher storage efficiency and bandwidth. Our study advances the practical applications of quantum memory devices based on REI-doped crystals.