Erbium atoms are integrated into silicon crystals for the first time and are expected to become an ideal component for future quantum networks

Artistic rendering of the latest experiment in which erbium atoms were integrated into a silicon chip. Image source: Max Planck Institute for Quantum Optics

For the first time, German scientists have integrated erbium atoms with special optical properties into silicon crystals. These atoms can be connected by light commonly used in communications, making them an ideal building block for future quantum networks. The latest experimental results were obtained without complex cooling and are based on existing silicon semiconductor production processes, making them suitable for building large quantum networks. Relevant research was published in the latest issue of the journal Physical Review X.

Quantum networks can be realized by using light to entangle individual carriers of quantum information - qubits - which can be built from individual atoms isolated from each other and embedded in a host crystal. In new research, scientists from the Max Planck Institute for Quantum Optics and the Technical University of Munich have demonstrated a feasible way to build quantum networks using atoms embedded within silicon crystals.

The latest technology relies on implanting erbium atoms into a silicon lattice under specific conditions. Research shows that erbium has good optical properties. The wavelength of infrared light emitted by its atoms is about 1550 nanometers, which is within the spectral range of data transmission in optical fiber cables. Erbium has low loss when propagating in optical fibers. In addition, the light emitted by erbium has excellent coherence, which is a prerequisite for quantum information storage and transmission. These properties make erbium a first choice for implementing quantum computers or for use as an information carrier in quantum networks.

But the big challenge was to embed the individual atoms of erbium in a repeatable way within the silicon crystal matrix and fix them in specific locations. To this end, the researchers first gave the erbium atoms a nanoscale fine structure, and then irradiated the silicon with an erbium ion beam, allowing individual atoms to penetrate and disperse to different places within the silicon crystal at high temperatures.

The relatively mild temperatures keep the individual erbium atoms firmly in place in the crystal lattice, rather than clumping together. Moreover, in previous experiments, erbium atoms showed excellent optical properties near absolute zero (minus 273.15 degrees Celsius), but in the latest research, scientists observed these properties at about 8 Kelvin (minus 265.15 degrees Celsius). Such a temperature is technically It is easy to implement and paves the way for future applications.