Telecom-Compatible Quantum Nodes via Erbium-Doped EuCl3
Rare-Earth Crystal Advancements Allow a Quantum Internet Compatible with Telecom Service
Telecom-Friendly Quantum Nodes
A multinational team of scientists created telecom-compatible quantum nodes using a dual-species rare-earth crystal, advancing global quantum communications. This research discusses how doping erbium ions into a europium-based host could improve optical interface and quantum storage.
The initiative involved the International Quantum Academy, Australian National University, and Shenzhen SUSTech experts. Quantum networking requires quantum repeaters that can store data for a long period and work with regular telecommunications infrastructure. Their research addresses this.
Quantum Gap Filling
A quantum internet uses quantum repeaters as relay stations to extend quantum messages over long fiber-optic cable distances. These repeaters require a platform to transmit and store quantum states with telecom wavelength photons.
The team employs erbium-doped stoichiometric EuCl3 ⋅ 6H2O crystals. Both rare-earth elements serve complimentary roles in this “dual-species” system. The scientific community knows europium's (Eu3+) extraordinary coherence, which is essential for long-term quantum storage. Erbium (Er3+) is ideal for optical interfacing with standard fiber networks due to its direct telecom-band emission and microwave compatibility.
“Frozen Core” Innovation
The study's discovery of a “frozen core” influence is surprising. The researchers used the spins of the erbium ions to shield the quantum states of the europium ions by cooling the crystal to 60 mK and applying a modest magnetic field of 0.1 T.
This raised Eu3+ optical coherence time from 62 to 162 microseconds, which the authors say is approaching the theoretical lifespan limit. This interaction enabled hour-long hyperfine state lifetimes, which are necessary for ultra-long-term quantum storage and may help satisfy the 10-hour criteria proposed in related high-performance research.
The researchers also measured the intensity of Er3+ and Eu3+ ion contact, which ranged from tens to hundreds of kilohertz. This interaction shifts the optical transition frequencies of europium ions, creating “satellite lines” in the absorption profile for accurate quantum control.
A Global Future Technology Collaboration
The team developed the project concept with F. Wang, R. Ahlefeldt, M. Sellars, and M. Zhong. At SUSTech, Mucheng Guo and Wanting Xiao spearheaded the experimental effort, while numerous Shenzhen and Canberra team members did theoretical modeling and analysis.
This project received financing from the National Natural Science Foundation of China and the National Science and Technology Primary Project of China. This investment shows the strategic importance of rare-earth materials in photonic quantum technology development.
Toward Quantum Network
The consequences of this work reach beyond the lab. The team has proven that combining the stabilizing and linking features of erbium and europium may develop a promising quantum node material.
Rare-earth-doped antiferromagnets and single erbium ions in solids have been studied, but the dual-species stoichiometric crystal can be used in telecom-compatible architectures. As safe, fast quantum communication becomes more important, these crystals could form a global quantum internet.
Researchers say these findings show rare-earth systems' exceptional potential for quantum information processing and its eventual usage in quantum repeaters and optics. As the study is finalized, scientists expect to integrate this dual-species platform into broader quantum networks.
