If aliens wanted to send us messages from 30 light years away, their best bet may be to use X-rays and quantum technology.
On Earth, researchers have previously encoded information into the quantum states of particles of light, or photons. Using the photons鈥� special properties, they have transmitted that information securely. Research teams have sent the data to other labs around the world 鈥� as a proof of concept for a quantum internet 鈥� and to satellites orbiting Earth.
and at the University of Edinburgh in the UK have shown that the technique could also work for interstellar data transmission, reaching planets outside of the solar system without the photons losing information along the way.
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The team used existing astronomical data and mathematical models to determine whether the photons might interact with other objects in space in a way that could destroy their quantum properties, which are crucial for secure communications.
One immediate concern was the gravitational fields of large planets or stars the photons may pass by, says 颁补濒诲别谤贸苍-Figueroa. The researchers also considered the effects of cosmic dust and solar winds, which could potentially disrupt the photons鈥� journeys.
Their calculations showed that the photons that make up X-rays may be able to preserve their quantumness, and therefore retain information very well, for tens of light years. Berera says that the photons鈥� path between about a hundred relatively nearby exoplanets and Earth probably wouldn鈥檛 present very disruptive obstacles.
鈥淚t鈥檚 maybe a happy circumstance that we live in a section of the interstellar space, which is actually quite under-dense relative to the average,鈥� he says.
at the University of Strathclyde in the UK says that space, which is mostly empty, is an inherently favourable medium for transmitting quantum information. Quantum communications networks on Earth have been limited in part because of information losses that happen when a photon moves through optical fibres, he says.
But there are still many technical challenges to be solved when it comes to transmitting quantum photons over interstellar distances, says at the University of Science and Technology of China. State-of-the-art technology on Earth has not, for instance, produced strong enough sources of quantum information to do this yet, he says.
Building receivers for quantum information coming from outer space would also require more guesswork than in terrestrial experiments where researchers know where the source of the information is, says at Sonneberg Observatory in Germany.
There are no known objects in space that naturally transmit signals with properties that could be mistaken for quantum encoded messages, but not just any quantum receiver could decipher alien messages, he says. Researchers would have to make assumptions about encryption codes or possibly infer them from some other kind of alien signal.
鈥淵ou could immediately say, 鈥榦h, there鈥檚 something an intelligent being sent here鈥�,鈥� says Berera. 鈥淎nd beyond that, of course, there鈥檚 lots of work ahead of us.鈥�
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