Since the correlations and entaglement doesnot last long enough when put through open air or even through optical fiber lines, researchers came up with ground-sattilite link for communicating quantum information across the globe. Since it minimizes the total light environment interaction by carrying out information transmission using free space. The first problem is to identify solutons that can resolve single photons on a sattilite. Researchers from china claim to built such a system to test this technology.
The underlying engineering solution is to explot avalanche breakdown in semiconductor chips and integrating it wiht other electronics on board. This is not a new technique but the contibutions of the work is how to shield it from the secondary and other heavy particles in outer space. This has opend up oppurtunities to try quantum and optical experiments in out space for the first time. Also this can enable communicating information across continents at some point of time.