The first modem for the quantum internet is already in development

Physicists at the Max Planck Institute for Quantum Optics have developed the basic technology for a new “quantum modem”. It will allow users to connect to a future quantum Internet based on the existing fiber optic network infrastructure.

The Otto-Hahn group “Quantum Networks” at the Max-Planck-Institute of Quantum Optics in Garching is investigating a “quantum modem”. The team has now achieved a first breakthrough in a relatively simple but highly efficient technology that can be integrated into existing fiber optic networks..

Delicate connection between quantum bits

The “quantum modem” is designed to efficiently establish a connection between flying and stationary qubits. For it, the team surrounding doctoral student Benjamin Merkel has developed a new technology and has just demonstrated its basic functionality.

Its fundamental advantage is that it could be integrated into the existing fiber optic telecommunications network. This would be the fastest way to advance a functional network of long-distance quantum technologies..

For this system to work, photons sent or received by the modem as carriers of quantum information must precisely match the infrared wavelength of the laser light used for telecommunications.

This means that the modem must have qubits at rest that can accurately react to these infrared photons with a quantum jump.. Only in this way can sensitive quantum information be transmitted directly between qubits at rest and flying qubits..

Extensive research by Garching's group showed that the element erbium is best suited for this purpose.. Its electrons can make a perfectly coincident quantum jump. Unfortunately, erbium atoms are very reluctant to make this quantum leap.

“You can think of it as a party, which should stimulate the best possible communication between, Let's say, ten guests. The size of the space is crucial here. In a football stadium the guests would get lost, a phone booth in turn would be too small”, continues the physicist, “but a living room would be nice”.


Garching's quantum modem remains purely fundamental research. But it has the potential to advance the technical realization of a quantum Internet..


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