Researchers from QuTech in Delft have succeeded in generating quantum entanglement between two quantum chips faster than the rate at which the entanglement is lost. Entanglement – once described by Einstein as spooky action — is the phenomenon that is to provide the power and security of a (future) quantum internet. Through a new, clever entanglement protocol and careful protection of the entanglement, the researchers, under the leadership of professor Ronald Hanson, are the first in the world to deliver such a quantum link 'on demand'. This opens the door to interconnecting multiple quantum nodes and with that the first real quantum network in the world. Their results were published in Nature.

Quantum internet

Through the application of quantum entanglement it is theoretically possible to build a quantum internet that is impossible to eavesdrop. But the building of such a quantum internet is an enormous challenge: you have to be able to create a reliable entanglement 'on demand' and then maintain it for a sufficient duration for this entangled information to arrive at the next node of the network. This has been, up to now, outside the reach of quantum experiments.

Scientists from QuTech in Delft are now the first to have experimentally generated entanglement from a distance of two meters – in a fraction of a second and 'on demand'; they then succeeded in maintaining this entanglement for a long enough period so that it (in theory) can be sent to a third node. 'The challenge is now to build a network of several entangled nodes: the first version of a quantum internet', states professor Hanson.

Higher performance

In 2015 the research group from Ronal Hanson already made the world news: they were the first to created quantum entanglement between electrons across a large distance (1.3 kilometres), providing proof of quantum entanglement. That experiment is the foundation of their current approach of developing the quantum internet: individual electrons in diamond chips at a distance of two metres are entangled, with photons as 'intermediaries'.

However, up to now, this experiment did not have the necessary performance to build a real quantum network. Hanson: 'In 2015 we could generate the connection once per hour, while the connection was maintained for only a fraction of a second. It was therefore impossible to add a third node to the network, let alone multiple nodes'.

Entanglement ‘on demand’

The researchers have now added multiple innovations to the experiment. Firstly, they demonstrated a new method of entanglement. This makes it possible to generate an entanglement between electrons at a rate of forty per second, over a distance of 2 metres. This is a thousand times faster than the old method. Combined with a clever way of protecting the quantum link from external noise, the experiment has now crossed a crucial threshold: for the first time an entanglement can be generated faster than that it is lost. Through technical improvements the experiment can now always generate 'entanglement on demand'.