An advanced alien civilization could send quantum signals to Earth.
Photons can be transmitted across vast, interstellar distances without losing their quantum nature, researchers report in Physical Review D.
It means that researchers searching for extraterrestrial signals could also be look for quantum messages.
Scientists are developing Earth-based quantum communications, a technology that uses quantum particles to establish communication and has the potential to be more secure than standard, or traditional communication systems.
Advanced extraterrestrial brings, if they are out there, may have adopted quantum communication as well, theoretical physicist Arjun Berera says.
A key obstacle in quantum communication is decoherence, in which a quantum particle loses its quantumness when interacting with its surroundings.
"The quantum states you normally think of are very fragile, and if there's some kind of external interaction, you may destroy that state" physicist Arjun Behra says.
Since the average density of matter in space is much lower than on Earth, particles can be expected to travel far before disintegrating. So Barrera and theoretical physicist Jaime Calderón Figueroa of the University of Edinburgh, calculated how far light – particularly, X-rays – can travel unhindered through interstellar space.
X-ray photons could more than traverse the Milky Way, potentially traveling hundreds of thousands of light-years or even more, the scientists found.
Based on the findings, Berera and Calderón Figueroa considered strategies to search for E.T.’s quantum dispatches.
One potential type of communication to search for is quantum teleportation, in which the properties of a distant particle can be transferred to another. Since the technology requires both quantum and classical signals, scientists could look for such simultaneous signals to identify any extraterrestrial quantum missives.