8. Conclusion

Quantum satellite communications mark a decisive milestone in the second quantum revolution, transforming fundamental physical concepts into hybrid infrastructures capable of securing and expanding information exchange on a global scale. As we have explored, quantum properties—such as superposition, entanglement, and non-cloning—applied to photons via polarization encoding not only overcome the limitations of terrestrial networks – —notably the losses that increase exponentially with distance in optical fibers – —but also pave the way for revolutionary applications: from quantum key distribution (QKD) for robust cybersecurity, to entanglement distribution for interconnecting entanglement switches and building advanced quantum information networks, as well as emerging services such as distributed quantum computing or quantum metrology.

Pioneering missions, such as...