The global pioneers in this area, namely the scientists led by Anton Zeilinger and Rupert Ursin of the University of Vienna and the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW) are also focusing on practical applications.
The absolutely eavesdrop-secure encoding of data is possible with the help of entanglement. A future data network could be based on the transmission of quantum information. A simple intercepting, reinforcing and transmitting of a signal, like the so-called repeaters do in our traditional Internet, cannot be duplicated in the quantum Internet. This would require a type of “quantum repeater.”
Now the scientists were able to realize such a repeater between stations of the European Northern Observatory located on the Canary Islands of La Palma and Tenerife. They worked with a total of four photons, of which two each originated from the same source.
In their experiment the researchers showed that the transmission (entanglement swapping) functioned over a distance of 143 kilometers in the turbulent atmosphere which actually interferes with the quantum state. “Because of this we are also optimistic that we will once be able to create a quantum cryptography network on a global scale”, Ursin says. The Earth is not enough. The researchers also want to transmit entangled states from satellites.