Breakthrough in quantum cryptography

A team from Austria's Institute for Quantum Optics and Quantum Information (IQOQI) managed to send entangled photons 144 kilometres (90 miles) between the Spanish islands of Las Palmas and the Balearics.

Because of the success of the test, the IQOQI team said it was now feasible to send this kind of unbreakable encrypted communication through space using satellites.

Quantum cryptography works by sending streams of light particles, or photons, making it entirely secure, as any eavesdropping would leave traces and immediately be detected.

In quantum cryptography, photons are used as the key for the encrypted communication -- just as mathematical formula are used in conventional cryptography.

The application of entangled photons on satellites and their distribution will allow us to test quantum mechanics over a distance of many thousand of kilometres. Albert Einstein and his colleagues discovered the “spooky action at a distance,” whereas the term “entanglement” found its way into quantum language and quantum information through the Austrian scientist Erwin Schrödinger.

With the development of novel ideas which produce more then 2. Mio. pairs of entangled photons per second, it is now possible to think seriously about the use of satellites. In this experiment, created by a team around Anton Zeilinger and Rupert Ursin, both photons were sent on a 144 km long journey from La Palma to Tenerife, before being received by the ESA ground station. The photons were exposed to the conditions they would find on the way from the satellite to earth. With that the feasibility of transmission from satellite to an optical ground station has been proven.

Indeed quantum cryptography is possible over a modern glass fibre net, but because of the high rate of transmission loss, this is limited to around 100 km. To realise future quantum communication networks on a global scale, satellite based systems must be developed and photons transmitted over optical free space distant from the ground. Therefore we are working in parallel with partners in the industry on the development of this source until capability in space is realised. If these preparations work to the schedule planned by the ESA, we can reckon on a start in space in the next decade.

From: Physorg.com