Modern telecommunications have revolutionised the way we communicate and quantum communications is the next evolution making us even more connected. First, quantum communication will provide a new secure ways for us to communicate with quantum encryption, or quantum key distribution. There are already optical fibre-based quantum networks established in Europe, and China and other regions. The next step to extending quantum communication range is to include a space segment. Establishing quantum network in space will also open up opportunities to study advanced physics such as the relativistic effects on quantum systems.
Our program at ANU is to build a continuous variable quantum network starting with a satellite-to-ground link with our partners the German Aerospace Center (DLR), NICT Japan and the Australian DST Group. For continuous variable system, the encryption key is encoded in the phase and amplitude quadrature sidebands of an optical beam. The laser field is then measured using a homodyne detectors adopting very similar methods to those found in classical communications. To reduce the losses and noise from a satellite-ground link, our plan is to implement advanced adaptive optics techniques used in astronomy in the optical ground station.