It is possible to transmit quantum signals, a new study proves. Quantum satellites could soon rely on transmitters installed on Earth, rather than generating signals in space.
Researchers have shown that it is possible to send quantum signals from Earth to satellites — and not just from space to groundas was believed until now. The advance could make global quantum networks much more powerful, accessible and practical.
Quantum satellites are mainly known for emitting entangled light particles (photons) from orbit to ground stations, a method used to create extremely secure communication links.
A new study now indicates that the process can also work not reverse sensewith quantum signals sent from Earth to a satellite — an approach until now considered impractical.
This conclusion eliminates several limitations important aspects of current quantum satellite systems. On land, the equipment can draw much more energy, is easier to maintain and allows generating much stronger signals.
These advantages could be decisive to build future networks that link quantum computers, using satellites as repeaters.
The work, led by physicists Simon Devitt e Alexander Solntsev and by a team from the University of Technology Sydney (UTS), was presented in a recently published in the journal Physical Review Research.
Quantum satellite communication has already made significant progress. The Chinese satellite Betterlaunched in 2016, managed for the first time to demonstrate the so-called , having sent, from space, data encrypted with quantum techniques.
In 2025, the Jinan-1 microsatellite took this work further by establishing one between China and South Africa.
Why bottom-up quantum communication was ruled out
“Current quantum satellites create intertwined pairs in space and then send each half of the pair to two locations on Earth — called downlink“, explains Professor Solntsev at UTS. “It is mainly used in cryptography, where a few photons are enough to generate a secret key.”
The opposite idea, producing entangled photons on Earth and transmit them to the topwas largely ignored. The idea seemed unrealistic due to expected losses, interference and scattering of light as it passes through the atmosphere.
“The idea is to fire two individual particles of light, from two separate ground stations, to a satellite orbiting 500 km above the Earth, traveling at around 20,000 km per hour, so that they meet with such precision that the quantum interference. Is this even possible?” asked Professor Devitt.
According to the new study, yes. “Surprisingly, our modeling showed that an uplink is viable. We include real-world effects, such as backlighting from the Earth and reflections of sunlight on the Moon, atmospheric effects and the imperfect alignment of optical systems,” he said.
Towards a scalable quantum internet
The team argues that the idea could soon be tested with receivers installed in drones or in balloonsas an intermediate step towards large-scale quantum networks, capable of connecting countries and continents, using small satellites in low orbit.
“A quantum Internet is a thing very different from current applications cryptographic technologies, still at an early stage. The underlying mechanism is the same, but it takes significantly more photons — more bandwidth — to power quantum computers,” said Devitt.
“In the future, quantum entanglement It will be a bit like electricity: a commodity that we talk about and that feeds other things. It is generated and transmitted in a form many times invisible to the user; we just turn on the devices and use it”, says the researcher.
“At the end, it will be the same with large quantum entanglement networks. There will be quantum devices that connect to an entanglement source, such as an energy source, using both to do something useful”, he concludes.
