Safer Quantum Communications with Infrared Light

An Italian research team has identified a new approach to make future quantum communications more reliable: using mid-infrared light. The study, conducted by the National Institute of Optics of the CNR in collaboration with the Italian Space Agency and published in Advanced Quantum Technologies, shows how this region of the light spectrum can improve the transmission of quantum information through the atmosphere.

Simulations demonstrate that mid-infrared light allows for more robust propagation of single photons, the elementary particles of light that carry quantum information, even in the presence of adverse environmental conditions such as fog and smog. This approach paves the way for more secure quantum links not only via optical fiber but also through the air, between buildings, ground stations, and potentially toward satellites.

Quantum communications represent a revolution in data transmission security because they exploit the properties of quantum mechanics. The fundamental idea originated in the 1980s, when it was discovered that light particles (photons) could be used to create cryptographic keys that are impossible to intercept without being detected. This occurs thanks to the quantum principle that measuring a quantum system inevitably alters it, thereby signaling any attempted espionage.

For decades, these communications were confined mainly to optical fibers, which, however, have distance limitations. For longer links, such as satellite connections necessary for secure global networks, transmission through the atmosphere is required. This is where the problem arises: the visible or near-infrared light traditionally used is easily absorbed or scattered by particles in the air, such as fog droplets or pollutants. Italian research starts precisely from this challenge, exploring a region of the spectrum – the mid-infrared – which interacts less with these obstacles, making more reliable transmissions possible even in difficult weather conditions.