Initial results from the world’s first quantum communications satellite Micius (Australasian Science, May/June 2017) launched last year have been published in Science, and show unequivocally that the strange phenomenon of “quantum entanglement” between pairs of light photons survives to distances of at least 1200 km. This greatly extends the previous record of 100 km and is another nail in the coffin of Einstein’s classical concept of physical reality. The results also strengthen the prospect of a secure global quantum internet that is immune to hacking.
A secure quantum link established between two parties, traditionally called “Alice” and “Bob” in the cryptographic literature, allows them to share a cryptographic key without fear of eavesdropping by a third party (“Eve”). This private key can then be used as a “one-time pad” to securely encrypt subsequent communications over an ordinary public network.
The new results show that a measurement of the state of one entangled photon by either Alice or Bob can instantaneously determine the outcome of a measurement by the other party, even though they may be separated by thousands of kilometres. Alice and Bob can...
