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arXiv · 2601.11879

Scalable and telecom single-erbium system with record-long room-temperature quantum coherence

Alex Kaloyeros·Natasha Tabassum·Spyros Gallis
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Abstract

Eliminating cryogenic operating requirements while preserving microsecond-scale quantum coherence and enabling CMOS scalability remains a central challenge for telecom quantum technologies. Addressing this, we introduce a CMOS-compatible quantum system comprising single-erbium-(Er)-ion qudits (five-level systems) operating across the visible and telecom C-band. Through innovative nanofabrication, we achieve self-aligned ion placement, enabling spatial isolation of single-Er ions and suppressing dephasing. We realize individually addressable single-Er-devices with record-long optical coherence times in the telecom C-band exceeding 500 {\mu}s at ambient conditions, a performance previously limited to vacuum conditions at temperatures over 900 times lower. Furthermore, we present the first demonstration of background-free, upconversion-enabled single-photon Er-emissions providing coherent, high-contrast optical readouts. This work showcases the first room-temperature single-Er-qudit system with unprecedented properties enabling next-generation cryogen-free telecom quantum technologies.

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Alex Kaloyeros, Natasha Tabassum, Spyros Gallis. 2026-01-17. Scalable and telecom single-erbium system with record-long room-temperature quantum coherence. https://arxiv.org/abs/2601.11879

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