Researchers all over the world are working to build a secure Internet based on the invisible quantum physical link between particles called entanglement. One of the main difficulties is that each additional node weakens the entanglement. Researchers from Delft and Oxford have now succeeded in forging a strong entanglement link from several weaker links. This breakthrough allows the first rudimentary quantum networks to be built in the near future, and it directly provides an essential component of a future quantum Internet.

Secure communication is one of the biggest challenges in the current digital era. All over the world, scientists are working on new methods to implement truly secure networks based on the principles of quantum mechanics. In such networks it is fundamentally impossible to eavesdrop without being noticed, but creating strong links in these networks, based on the powerful but fragile principle of quantum entanglement, is a major challenge.

The research group led by Ronald Hanson at QuTech is renowned for its implementation of links based on quantum entanglement. Using photons, the scientists are able to link quantum information over macroscopic distances up to one kilometer. The researchers previously demonstrated the power of this sort of link: the entanglement is invisible to intermediate parties, and the information is safe against eavesdropping.

Ronald Hanson: “Now we are taking an important additional step. We previously achieved entangled information between two electrons in two diamonds, and now we are also using one of the nuclear spins present in each diamond to temporarily store the entangled information.” With the information stored safely, the researchers can entangle the electrons again. Then there are two links. They can be cleverly combined to create a single stronger entangled link from the two weaker links, which the researchers compare to distilling whisky from basic ingredients with lower alcohol content. This method opens important doors for the quantum internet.