Hanson team improves entanglement by distillation

Previously, the Hanson Lab demonstrated the entanglement of two electrons over a large distance. Now they have shown how to combine entanglement in a process they call distillation.

Ronald Hanson with co-authors Peter Humphreys and Norbert Kalb (Photo: Marieke de Lorij)

Dr. Ronald Hanson and his team at QuTech (Faculty of Applied Sciences) became famous by demonstrating an error with Einstein’s work. Their sophisticated experiment demonstrated entanglement of two electrons in diamond chips on two opposite sides of the campus. In 2015, their Loophole-free Bell test was published in Nature.

The instantaneous communication between two distant entangled quantum bits proved to be real, even though Einstein had always rejected it as ‘spooky actions’.

Now, less than two years after that ground-breaking experiment, the Hanson team has published another demonstration.

Store the information

According to Ronald Hanson, “Whereas we first realised entangled information between two electrons in diamonds, we now also are using one of the nuclear spins present in each diamond to temporarily store the entangled information.”

With the information stored safely, the scientist can entangle the electrons again.

“Now we have two entanglement links. By combining these in a smart way, we manage to generate one strongly entangled link out of the two weaker entangled links, just like distilling whisky out of lower-alcoholic ingredients. In principle, this process of entanglement distillation can be repeated over and over, until high-quality entanglement is obtained,” said Hanson.

Step towards the quantum internet

He regards the experiment as a step towards the quantum internet that is inherently safe because no-one can eavesdrop on entangled qubits.

“We could now entangle electrons in additional quantum nodes such that we can extend the number of networking links towards a first real quantum network,” said Hanson.

The first demonstration of a quantum internet might be closer than you might think. According to Hanson, “In five years we will connect four Dutch cities in a rudimentary quantum network.”

-> N. Kalb, A. A. Reiserer, R. Hanson et. al. Entanglement Distillation between Solid-State Quantum Network Nodes, Science magazine, June 1, 2017

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