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

TL;DR

This paper introduces a CMOS-compatible single-erbium-ion quantum system operating at room temperature with record-long coherence times, enabling scalable telecom quantum technologies without cryogenic cooling.

Contribution

The work demonstrates a novel, scalable, room-temperature erbium-based quantum system with long coherence times and high-fidelity optical readout, advancing telecom quantum tech.

Findings

Achieved single-Er-ion devices with coherence times over 500 μs at room temperature.

First demonstration of background-free, upconversion-enabled single-photon emissions from Er.

Enabled spatially isolated, individually addressable Er-ion qudits compatible with CMOS fabrication.

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.