If the test of 30-40 km secure quantum communication succeeds, it will become the world's longest secure free-space quantum teleportation so far.
Dr. Pan Jianwei, a world renowned Chinese quantum physicist and professor at the University of Science and Technology of China, is leading a research group to do the test on the Great Wall.
Pan told Xinhua Monday that the test is prepped for longer distance quantum teleportation using quantum signals transmitted through satellites to receivers more than ten thousand kilometers away, and a global network is to be set up for quantum communication through which worldwide secure communication can be achieved.
Pan said if information is encoded in quantum state it may outperform classical communication systems in terms of absolute security, efficiency and channel capacity.
He said any listener-in trying to get photons can be detected immediately since the disparity between input and output codes would change photon polarization, which would report an insecure communication.
Pan's group, which has long been dedicated to cutting-edge quantum communication, took the lead in "experimental demonstration of five-photon entanglement and open-destination teleportation," according to the British journal Nature issue of July 1, 2004, "a breakthrough in quantum computation and quantum communication network".
"Current technologies can only achieve 20km secure quantum teleportation. The 100km-or-longer quantum telepathy still remains insecure," said Pan who added that 100km secure communication may become true within two years.
He said noise is inevitable in quantum transmission, therefore, to prove the transmission absolutely secure against noisy background is first and foremost.
He said any classical code system can be insecure since it has never been proved mathematically.
Quantum code systems are of absolute security theoretically no matter how advanced a classical or quantum computer eavesdroppers have. Quantum encoding systems only needs apparatus of quantum transmission and measurement instead of expensive quantum computers, added Pan.
Pan's five-photon entanglement marks the world's first instance of five-particle entanglement and a hidden transmission between terminal quanta. The finding secures China a leading position, ahead of the United States, France and Austria in quantum entanglement research.
(Xinhua News Agency November 29, 2005)
