Satellite-based Quantum Network: Security and Challenges over Atmospheric Channel

The ultra-secure quantum network leverages quantum cryptography to deliver
unsurpassed data transfer security. In principle, the well-known quantum key
distribution (QKD) achieves unconditional security, which raises concerns about
the trustworthiness of 6G wireless systems in order to mitigate the gap between
practice and theory. The long-distance satellite-to-ground evolving quantum
network distributes keys that are ubiquitous to the node on the ground through
low-orbit satellites. As the secret key sequence is encoded into quantum
states, it is sent through the atmosphere via a quantum channel. It still
requires more effort in the physical layer design of deployment ranges,
transmission, and security to achieve high-quality quantum communication. In
this paper, we first review the quantum states and channel properties for
satellite-based quantum networks and long-range quantum state transfer (QST).
Moreover, we highlight some challenges, such as transmissivity statistics,
estimation of channel parameters and attack resilience, quantum state transfer
for satellite-based quantum networks, and wavepacket shaping techniques over
atmospheric channels. We underline two research directions that consider the
QST and wavepacket shaping techniques for atmospheric transmission in order to
encourage further research toward the next generation of satellite-based
quantum networks.