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

This article presents a groundbreaking approach to scalable, room-temperature quantum systems using single erbium (Er³⁺) ions as qudits (multi-level quantum systems). The system operates in the telecom C-band, a key wavelength range for quantum communication. This work focuses on the challenges of maintaining quantum coherence at room temperature and developing a system that is compatible with CMOS fabrication, which is crucial for scaling quantum technologies.

Key Highlights:

1. CMOS-Compatible Quantum System: The authors introduce a single-Er³⁺ ion qudit system based on erbium ions embedded in silicon carbide (SiC) nanostructures, which can operate at room temperature in the telecom C-band. This system is scalable and compatible with semiconductor fabrication, which has been a major limitation for previous quantum systems that require cryogenic temperatures.

2. Innovative Nanofabrication: A novel non-lithographic approach for defining nanostructures with dimensions less than 5 nm allows for precise control of ion placement. This technique ensures spatial isolation of individual Er³⁺ ions, reducing decoherence caused by ion-ion interactions and environmental noise.

3. Record-Long Coherence Times: The integration of these single-Er³⁺ ions in SiC nanostructures allows for unprecedented room-temperature optical coherence times exceeding 500 microseconds, which was previously achievable only under cryogenic conditions. This opens up possibilities for practical quantum applications without the need for cooling systems.

4. Single-Photon Emission and Coherent Optical Control: The system achieves background-free, high-contrast optical readouts via upconversion, where single-photon emissions from Er³⁺ ions are detected with high efficiency. Rabi oscillations and Ramsey coherence measurements demonstrate coherent control of these ions at room temperature, with T₂ coherence times reaching 568 microseconds.

5. High-Efficiency Single-Photon Sources: The article showcases the first room-temperature, telecom-band single-photon emitters from Er³⁺ ions, with high-quality photon emission characteristics. These results are critical for applications in quantum networking, secure communications, and quantum sensing.

Conclusion:

The work introduces a scalable, CMOS-compatible quantum system based on single-Er³⁺ ions that exhibit record-long coherence times at room temperature. This achievement breaks through several technical barriers in quantum information science, offering a practical path for integrating these systems into real-world quantum technologies. It has the potential to revolutionize quantum sensing, communication, and computing by enabling cryogen-free, telecom-compatible quantum devices.