They reach a new milestone in the quantum internet

Inspenet, March 30, 2023

The new experiment translates quantum information between different technologies, in an important step for the quantum internet and many other advanced technological applications.

Research led by the University of Illinois Urbana-Champaign developed a new way to “translate” quantum information between different types of quantum technologies, with significant implications for quantum computing, communication, and networking. The researchers succeeded in converting quantum information from the format used by quantum computers to the format needed for quantum communication.

Problems with quantum networks

“Many of the technologies we use for classical communication — cell phones, Wi-Fi, GPS, and the like — use microwave light frequencies,” said Aishwarya Kumar of the University of Chicago and lead author of the study. “But you can’t use that for quantum communication because the quantum information you need is in a single photon, and at microwave frequencies that information will be buried in thermal noise,” he explained.

For this reason, if you want to build a quantum network or connect quantum computers, you cannot send microwave photons, as the quantum information is too weak to survive the journey. Transferring the quantum information to a higher frequency photon, called an ‘optical photon’, which is much more resistant to environmental noise, could be the solution. But, since information cannot be transferred directly from photon to photon, we need intermediate matter.

The solution between atoms and closed chambers

The novel technology, developed by Kumar’s team, exploits the ability of the rubidium atom’s electrons to perform two quantum leaps in their energy levels, emitting their respective individual photons. One jump is exactly equal to the energy of a microwave photon and the other is exactly equal to the energy of an optical photon.

By using lasers to shift the energies of the electrons up and down, they cause the atom to absorb a microwave photon with quantum information, and then emit an optical photon with that quantum information. This translation between different modes of quantum information is called ‘transduction’ and it works both ways. The researchers used a superconducting cavity, with tunnels intersecting in a very specific geometry, to force the photon to bounce around in an enclosed space. This strengthens the interaction between the photon and whatever matter is placed within it.

“One of the things that we’re really excited about is the ability of this platform to generate really efficient entanglements,” Kumar said. “Entanglement is fundamental to almost everything quantum we care about, from computing to simulations, metrology and atomic clocks. I’m excited to see what else we can do,” he stressed. The results were published this Wednesday in the journal Nature .

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Photo : A niobium superconducting cavity. The holes lead to tunnels that intersect to trap light and atoms. Credit: Aishwarya Kumar

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