December 1, 2022


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Erbium atoms are bound to silicon.  This is the best filter for quantum networks known to us

Erbium atoms are bound to silicon. This is the best filter for quantum networks known to us

Scientists from the Max Planck Institute for Quantum Optics They specialize in integrating erbium atoms with silicon crystals – an ideal building block for quantum networks. Since the same process can be implemented using known semiconductor fabrication methods and without advanced cooling, this could be a step that will push quantum computing to a new path. Details are described in the magazine X . physical review.

Quantum networks are getting closer

Connecting quantum computers will give us entirely new possibilities. The leap could be even greater than with the advent of the “classic” internet. A team of scientists from the Max Planck Institute for Quantum Optics (MPQ) in Garching and the Technical University of Munich has demonstrated a feasible method for constructing a quantum network using atoms in a silicon crystal. What does this mean for us? The same technology used to produce pure computers can be used to develop quantum computers.

Andreas Gretsch during the experiment / photo. MPQ

The new technique is based on erbium atoms, which are deposited in the silicon crystal lattice under very specific conditions.

We learned from previous experiments that erbium has good optical properties for such an application. Atoms of this element emit infrared light with a wavelength of about 1,550 nanometers – the spectral range used to transmit data in optical fibers. It shows only slight propagation losses in the light-carrying fibres. Moreover, the light emitted by erbium has excellent coherence. These properties make erbium an excellent candidate for developing quantum computers or for use as an information carrier in a quantum network.Dr. Andreas Risserer, Head of the Otto Hahn Quantum Networks Research Group at MPQ

However, for the integration of erbium atoms with silicon to be possible, it was first necessary to give it nanometric structures that act as light-conducting elements. Physicists irradiated silicon with a beam of erbium ions, thanks to which individual atoms penetrated and dispersed in different places at high temperatures.

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Contrary to the usual procedure, we did not heat the chips to 1000 degrees, only a maximum of 500 degrees Celsius. The result of the relatively mild temperature was the particularly stable integration of single erbium atoms into the crystal lattice, without more atoms clumping together. This was demonstrated in very narrow spectral lines in the emission of infrared light by erbium, at about 10 kHz. It is also a useful property for building a quantum network.Andreas Gretsch, PhD student at MPQ

The range of possible applications for future quantum networks is huge. They can be used to build quantum computers with a large number of separate and connected processors. Quantum networks can be used to study the properties of new types of materials or used to build something like a quantum internet.