Long-lived quantum memories with rare-earth ions doped in crystals

Abstract:Quantum memory is a core enabling device for large-scale quantum networks, serving as the fundamental building block for quantum repeaters and transportable quantum memories. Among various physical platforms, rare-earth-ion-doped crystals stand out as one of the most promising solid-state candidates for long-lived photonic quantum memories, owing to their exceptionally long spin coherence time and their compatibility with integration. In this review, we first introduce the physical mechanisms underlying long-lived spin coherence in rare-earth systems, with particular emphasis on the zero-first-order-Zeeman transition and dynamical decoupling techniques. We then review the experimental progress in this field, highlighting three distinct lifetimes--the spin coherence time, the light storage time, and the quantum storage time--and covering experiments that have achieved hour-scale spin coherence, minute- to hour-scale light storage, and minute-scale single-photon-level quantum storage. Finally, we discuss the remaining challenges that hinder the realization of practical long-lived quantum memories, explore potential strategies to overcome these obstacles, and outline the prospects for their future applications in quantum networks.

The incorrect value 4.14 on page 7 of the published version has been corrected to 1.16

arXiv:2611.04526 [quant-ph]

(or arXiv:2611.04526v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2611.04526 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

https://doi.org/10.1007/s44214-026-00110-1 Focus to learn more DOI(s) linking to related resources

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