Quantum-limited measurements of optical signals from a geostationary satellite
This work addresses the challenge of establishing global secure quantum communication networks, though it appears incremental as it builds on existing quantum communication concepts with a new distance demonstration.
The researchers tackled the problem of measuring quantum optical signals over extremely long distances by performing quantum-limited coherent measurements of signals sent from a geostationary satellite 38,600 km away, bounding excess noise to demonstrate the feasibility of quantum communication in this scenario.
The measurement of quantum signals that traveled through long distances is of fundamental and technological interest. We present quantum-limited coherent measurements of optical signals, sent from a satellite in geostationary Earth orbit to an optical ground station. We bound the excess noise that the quantum states could have acquired after having propagated 38600 km through Earth's gravitational potential as well as its turbulent atmosphere. Our results indicate that quantum communication is feasible in principle in such a scenario, highlighting the possibility of a global quantum key distribution network for secure communication.