A quantum node device that might pave the way for a future space-based quantum Internet has been successfully tested for the first time aboard a small satellite.
The device, called SPEQS, has been developed by a team from the National University of Singapore (NUS) and the Glasgow-based University of Strathclyde. It contains technology for creation of the so-called correlated photons, which are a precursor for the better known entangled photons that communicate across large distances.
In an article published in the latest issue of the journal Physical Review Applied, the team led by NUS researcher Alexander Ling described first result of the experiment, which saw the SPEQS system reliably creating and measuring pairs of photons with correlated properties.
“This is the first time anyone has tested this kind of quantum technology in space,” Ling said.
The researchers envision that in future, such systems would be creating entangled photons and use them to communicate across large distances through quantum networks consisting of ground-based and space-based nodes. Such a network could connect powerful quantum computers and create and transmit unbreakable keys for secret messaging.
Quantum networks on Earth already exist, but are considerably limited. Distance is a major obstacle in sharing information through entangled photons; up to a few hundred kilometres will give the best result.
“Alex and his team are taking entanglement, literally, to a new level,” said Professor Artur Ekert, Director of The Centre for Quantum Technologies at NUS, who invented the idea of using entangled particles for cryptography.
“Their experiments will pave the road to secure quantum communication and distributed quantum computation on a global scale.”
The whole SPEQS device fits into a nanosatellite the size of a shoe box. At its heart is a BluRay laser, which splits photons in two and measures their properties. The system, complete with a laser diode and a set of crystals, mirrors and photon detectors, is placed inside an aluminium block and attached to a printed circuit board 10 by 10 cm in size.
The researchers believe that quantum technology in space would work better than in terrestrial conditions as it would encounter less obstruction from the Earth’s atmosphere.
The payload’s journey to space was quite complicated. The satellite was originally aboard Orbital’s Cygnus 3 space capsule, which was destroyed during a launch pad explosion in October 2014. The SPEQS system, however, was found intact on a nearby beach after the blast.
The researchers plan to soon launch a system producing actual entangled photons and follow with experiments that would attempt to send entangled photons to Earth and other satellites.