(InsideQuantumTechnology.BLOG)  An explanation of the need for both fiber and satellites for quantum communications to be scaled globally.  Both can transmit qubits, but for now in the world of the “Quantum Internet”, fiber and satellites serve two different markets and represent two different opportunities.  Read more in the in-depth, information-dense companion blog to your ITQ newsletter.
Optical losses set a restriction on the distance at which fiber QKD can work effectively. For now, the record is 421 km, which was set by ID Quantique in November 2018. Simulations show that fiber-transmitted QKD at greater than 500km will make the results of little practical use. Until quantum repeaters become a commercial reality, long haul QKD will be satellite based. The dominant scientific reality here is that even in the best-case scenarios fiber has losses around 0.2dB/km, while the atmosphere is practically transparent to photons. Satellite QKD does come with its disadvantages. Secure keys can be generated only during uninterrupted ground-to-sky contact, limiting the amount of time during the day when a satellite can be active. This is somewhat resolvable by launching satellites at higher orbits.
To learn more about the potential of fiber and satellite QKD, and quantum technology in general, visit the Inside Quantum Technology Conference, which will be held at the Hynes Convention Center, Boston, March 19-21. Also, please note that Inside Quantum Technology will be publishing a report on QKD Markets in March.
Meanwhile, stay tuned and watch the InsideQuantumTechnology.com/blog space for valuable, technical discussions integrating the science and business of quantum technologies.