We argue that long optical storage times are required to establish entanglement at high rates over large distances using memory-based quantum repeaters. Triggered by this conclusion, we investigate the $795.325{\mathrm{nm}}^3$ ${\mathrm{H}}_6\leftrightarrow {{}^3\mathrm{H}}_4$ transition of $\mathrm{Tm}:{\mathrm{Y}}_3{\text{Ga}}_5{\mathrm{O}}_{12}$ (Tm:YGG). Most importantly, we find that the optical coherence time can reach 1.1 ms, and, using laser pulses, we demonstrate optical storage based on the atomic frequency comb protocol during up to $100\mu \mathrm{s}$ as well as a memory decay time $T_m$ of $13.1\mu \mathrm{s}$. Possibilities of how to narrow the gap between the measured value of $T_m$ and its maximum of $275\mu \mathrm{s}$ are discussed. In addition, we demonstrate multiplexed storage, including with feed-forward selection, shifting and filtering of spectral modes, as well as quantum state storage using members of nonclassical photon pairs. Our results show the potential of Tm:YGG for creating multiplexed quantum memories with long optical storage times, and open the path to repeater-based quantum networks with high entanglement distribution rates.

• Received 4 June 2021
• Accepted 20 October 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.220502