Entangled atoms over distance pave way for future quantum networks

Scientists have entangled two ions over a distance of 230 metres, according to a new study.

Trapped ions have previously only been entangled in one and the same laboratory.

The experiment at the University of Innsbruck, Austria, has showed that trapped ions are a promising platform for future quantum networks that span cities and eventually continents, the study said.

The latest results have been published in the journal Physical Review Letters.

According to the study, trapped ions are one of the leading systems to build quantum computers and other quantum technologies.

To link multiple such quantum systems, interfaces are needed through which the quantum information can be transmitted, the study said.

In recent years, researchers led by Tracy Northup and Ben Lanyon at the University of Innsbruck's Department of Experimental Physics have developed a method for doing this by trapping atoms in optical cavities such that quantum information can be efficiently transferred to light particles, the study said.

The light particles can then be sent through optical fibres to connect atoms at different locations, the study said.

Now, their teams, together with theorists led by Nicolas Sangouard of the Université Paris-Saclay, France, have for the first time entangled two trapped ions more than a few metres apart, the study said.

According to the study, the two quantum systems were set up in in two laboratories, one in the building that houses the Department of Experimental Physics and one in the building that houses the Institute of Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Austria.

''Until now, trapped ions were only entangled with each other over a few metres in the same laboratory.

''Those results were also achieved using shared control systems and photons, or light particles, with wavelengths that aren't suitable for travelling over much longer distances,'' explained Lanyon.

After years of research and development, the Innsbruck physicists have now managed to entangle two ions across campus, the study said.

''To do this, we sent individual photons entangled with the ions over a 500-metre fibre optic cable and superimposed them on each other, swapping the entanglement to the two remote ions,'' said Northup, describing the experiment.

''Our results show that trapped ions are a promising platform for realizing future distributed networks of quantum computers, quantum sensors and atomic clocks,'' said Northup.

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