Improved Security Analysis for Quantum Communications from Space

(QuantumLab.org) The properties of light particles can create shared quantum keys for secure communication – but ensuring a key’s security takes more than just measuring the photons. Singapore’s Center for Quantum Technology’s (CQT) Charles Lim and Artur Ekert report with experimentalist colleagues from China a more efficient security proof method for short keys.
The improved analysis could be particularly useful for satellite-based quantum communication systems, which typically operate with slower data rates than their terrestrial counterparts.
Generating a quantum-secure key from raw measurement data involves a series of technical calculations. Charles’ group is developing a quantum-safe technology known as measurement-device independent QKD over optical fibre networks. He notes that they aim to generate one megabit of secret key per second in real time, which will require collecting hundreds of millions of measurement points equally fast.
However, in the case of satellite-based QKD, data rates are smaller. To consider how to deal with that, Charles and Artur worked with Feihu Xu and Jian-Wei Pan, two members of the team behind China’s Micius quantum satellite, which has sent pairs of entangled photons from space to ground stations more than 1000km apart. They are affiliated with the University of Science and Technology of China in Hefei and in Shanghai.
At CQT, where Charles is a Principal Investigator, he has discussed the work with colleague Alexander Ling, whose group has a quantum nanosatellite called SpooQy-1 in orbit. Alexander plans to use the methods. He points out that it will also be useful in another model of satellite communication. Instead of the satellite being in contact with two ground stations simultaneously, it can create keys by doing quantum communication with one ground station at a time, then sending some classical signals. This would give a higher block size to start from.