Scientists create first-ever working quantum network

12 Apr 2012

Single atoms form the nodes of an elementary quantum network in which quantum information is transmitted via the controlled exchange of single photons. Graphic courtesy of the Max Planck Institute of Quantum Optics and Andreas Neuzner

A group of scientists from the Max Planck Institute of Quantum Optics in Germany say they have built the world’s first elementary quantum network based on interfaces between single atoms and photons.

The scientists’ research findings have been published in Nature today.

The researchers said they believed they had made a breakthrough in quantum communication.

The scientists were part of a group of Prof Gerhard Rempe, director at the Max Planck Institute of Quantum Optics and head of the Quantum Dynamics division.

The elementary quantum network they have pioneered apparently consists of two coupled single-atom nodes that communicate quantum information via the coherent exchange of single photons.

“This approach to quantum networking is particularly promising because it provides a clear perspective for scalability,” said Rempe today.

Drawing on how we rely on sophisticated networks all the time, be it to phone a friend or trawl the internet, with data being transferred at the speed of light between different nodes, the scientists spoke of the huge challenge to build corresponding networks for the exchange of quantum information.

Quantum leap?

They said these future quantum networks could have the potential to give insights into fundamental questions in physics, as well as having applications in secure communication and the simulation of complex many-body systems. They said such quantum networks could also be used for distributed quantum computing.

Rempe’s Quantum Dynamics group of scientists have spent many years working on systems in which single atoms are embedded in optical cavities. They embarked on this research following a proposal from Prof Ignacio Cirac, director at the institute.

Stephan Ritter, leader of the experiment, said quantum networks have peculiar properties not found in their classical counterparts and that this was down to the fundamentally different behaviour of the exchanged information.

While a classical bit represents either 1 or 0, a quantum bit can take both values at the same time in a phenomenon called coherent superposition, according to the group.

“We were able to prove that the quantum states can be transferred much better than possible with any classical network. In fact, we demonstrate the feasibility of the theoretical approach developed by Cirac,” said Ritter.

Carmel Doyle was a long-time reporter with Silicon Republic