Quantum-limited measurements of optical signals from a geostationary satellite

TL;DR

This paper demonstrates quantum-limited measurements of optical signals from a geostationary satellite, showing the feasibility of global quantum communication despite atmospheric and gravitational noise.

Contribution

It provides the first bound on excess noise for quantum signals over 38,600 km, supporting the potential for satellite-based quantum key distribution.

Findings

Quantum signals can be measured at geostationary distances with minimal excess noise.

Results support the feasibility of a global quantum communication network.

Quantum communication remains viable despite Earth's atmosphere and gravity effects.

Abstract

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.