Rare earth quantum memories embedded in photonic integrated circuits

Quantum communication networks promise ultra-secure data transmission, but current systems are limited by the short distances single photons can travel—typically tens of kilometres in fibre or line-of-sight via satellite. To extend this range, quantum repeaters are needed, and at their core lie quantum memories. However, existing quantum memories rely on bulky, free-space optics and lack integration with scalable photonic platforms.

This project addresses that gap by embedding rare-earth quantum memories into photonic integrated circuits (PICs), enabling compact, scalable, and high-performance quantum repeaters. Key challenges include maintaining optical alignment at cryogenic temperatures and achieving strong light-matter interaction without damaging delicate crystal structures.

The project pioneers a hybrid architecture where light is routed through cryogenically cooled rare earth-doped crystals using advanced photonic chips. The project will combine high-speed electro-optic modulation with long-lived quantum storage, paving the way for multiplexed quantum memories and scalable repeater nodes.

The team from Korea’s Advanced Institute of Science & Technology (KAIST), brings world-class expertise in photonic integrated circuits, including high-speed modulators, multiplexers, and scalable PIC architectures. From New Zealand, Associate Professor Jevon Longdell of the University of Otago is internationally recognized for his pioneering work in rare-earth-doped quantum memories. Together, they will co-develop scalable quantum repeater technologies that neither country could achieve alone.