New distance record for quantum communication

A quantum communication has been sent across a record 144 kilometres (90 miles) using a process which may one day be used to send secret messages across space via a network of satellites.

Quantum teleportation involves "entangling" two particles so that any change to the state of one also occurs instantly in its twin, wherever it may be.

The researchers entangle a pair of photons and then fire a single photon at one of the pair. The resulting interaction changes the state of both entangled photons, effectively teleporting a quantum bit of information - known as a qubit - from one place to another.

The entangled photons behave "like psychic twins", the researchers say: even if they are far apart, a disturbance to one affects the other - an oddity that Albert Einstein dubbed "spooky interaction."

Marked improvement

In the experiment, polarisation-entangled photon pairs were generated on Roque de los Muchachos, a mountain observatory on the island of La Palma in Spain's Canary Islands.

While one photon stayed in La Palma, its twin was sent over an optical free-space link to Tenerife about 144 kilometres away, where the Optical Ground Station of the European Space Agency acted as a receiver. It was a marked improvement over the 13-km distance achieved earlier in a similar.

The international team of researchers were able to generate a quantum cryptographic key over 144 km.

They described their experiment as "an essential first step towards future satellite-based quantum communication and experiments on quantum physics in space".