Researchers at the University of Technology Sydney (UTS) have developed a new method for sending once-impossible Earth-to-space quantum light transmissions, which could enable ultra-secure satellite communications in the future.
The technology produces a beam of entangled light particles, a feat previously achieved only in the space-to-ground direction. The UTS team revealed their advances in a paper recently published in Physical Review Research.
Quantum Communications
China has been operating space-based quantum communications for almost a decade, beginning with the Micius satellite in 2016. Subsequently, the Jinan01 satellite, launched this year, established a 12,900-kilometer quantum link connecting China to South Africa.
“Current quantum satellites create entangled pairs in space and then send each half of the pair down to two places on Earth – called a ‘downlink, ‘” said co-author Professor Alexander Solntsev. “It’s mostly used for cryptography, where only a few photons (particles of light) are needed to generate a secret key.”
In previous estimates, scientists believed that moving in the opposite direction would be impossible, as signal loss, interference, and scattering would degrade the uplink. Despite these issues, ground station transmitters have many advantages over satellite-based ones. They have easier access to power, enabling them to produce stronger signals while also being far easier to maintain.
By developing uplink technology, the researchers believe it will allow satellite-connected quantum computer networks, pushing them to overcome the challenges involved. Their first step was to create a testable concept that addressed the interference issues, which they did.
“The idea is to fire two single particles of light from separate ground stations to a satellite orbiting 500 km above Earth, travelling at about 20,000 km per hour, so that they meet so perfectly as to undergo quantum interference,” said co-author Professor Simon Devitt. “Is this even possible?”
Hellbound and Down 