Entangled atoms traverse the quantum network from lab to lab

Trapped ions are one of the main systems for building quantum computers and other quantum technologies. To link several of these quantum systems, interfaces are needed through which quantum information can be transmitted. In recent years, researchers led by Tracy Northup and Ben Lanyon from the Department of Experimental Physics at the University of Innsbruck have developed a method to achieve this by trapping atoms in optical cavities so that quantum information can be efficiently transferred to light particles. The light particles can then be sent through optical fibers to connect atoms in different places. Today, their teams, along with theoreticians led by Nicolas Sangouard from the University of Paris-Saclay, have for the first time entangled two ions trapped more than a few meters apart.

Platform for building quantum networks

The two quantum systems were installed in two laboratories, one in the building that houses the Department of Experimental Physics and the other in the building that houses the Institute for Quantum Optics and Quantum Information of the Austrian Academy Sciences. “Until now, the trapped ions were only entangled with each other for a few meters in the same laboratory. These results were also obtained using shared control systems and photons (light particles) with wavelengths that are not suitable for traveling much longer distances,” explains Ben Lanyon. After years of research and development, physicists in Innsbruck have now succeeded in entangling two ions on campus. “To do this, we sent individual photons entangled with the ions down a 500-meter fiber optic cable and superimposed them on each other, swapping the entanglement to the two distant ions,” says Tracy Northup, describing the ‘experience. “Our results show that trapped ions are a promising platform for realizing future distributed networks of quantum computers, quantum sensors and atomic clocks. »

Ben Lanyon and Tracy Northup’s teams are part of the Quantum Internet Alliance, an international project under the European Union’s Quantum Flagship. The latest results have been published in Physical examination letters. The research was financially supported by the Austrian Science Fund FWF and the European Union, among others.