Programmable cavity-enhanced telecom quantum memory in thin-film lithium niobate

TL;DR

This paper demonstrates a cavity-enhanced quantum memory in erbium-doped thin-film lithium niobate, enabling efficient, programmable, and spectrally multiplexed quantum storage and routing of telecom photons with verified quantum entanglement preservation.

Contribution

It introduces a novel integrated erbium-doped lithium niobate quantum memory with high efficiency, fast spectral control, and quantum entanglement preservation capabilities.

Findings

Achieved 23.3% on-chip storage efficiency for 100-ns storage.

Enabled frequency-selective routing of photons at rates up to 20 MHz.

Stored and retrieved entangled telecom photons, violating entanglement bounds by over 11 standard deviations.

Abstract

Spectrally multiplexed telecom quantum networks require quantum memories that combine efficient storage with programmable frequency addressing. An ideal integrated implementation should therefore unite a native telecom transition, efficient storage and fast on-chip spectral control. Here we demonstrate a cavity-enhanced quantum memory in an isotopically purified $^{167}\mathrm{Er}^{3+}$-doped thin-film lithium niobate microring resonator. Long-lived hyperfine shelving states support persistent, high-contrast atomic frequency comb preparation, with a single-component comb lifetime of $277.6 \pm 52.6$s. Together with cavity impedance matching, this yields an on-chip storage efficiency of $23.3 \pm 0.5\%$ for 100-ns storage. The intrinsic electro-optic response of lithium niobate enables frequency-selective storage and routing of retrieved photons at rates up to 20~MHz with inter-channel crosstalk below $10^{-4}$. We further store and retrieve time-energy-entangled telecom photons, violating an entanglement-witness bound by more than 11 standard deviations and thus verifying the quantum nature of the storage process. Our results establish erbium-doped thin-film lithium niobate as a programmable light--matter interface for spectrally multiplexed quantum networks.