In the bizarre field of quantum physics, quantum entanglement, what Einstein called “creepy action at a distance,” stands out as one of the most intriguing phenomena. And now scientists have successfully demonstrated it again, this time aboard a CubeSat satellite that orbits Earth.
Quantum entanglement is where two particles inextricably come together over a distance, so that one serves as an indicator of the other in a certain way. That unbreakable link could one day form the basis of a super fast and super secure quantum internet.
While a quantum internet is still a long way off, if we want it to work it will require more than just fiber optics.
Therefore, scientists are experimenting with quantum entanglement in all sorts of new and improved ways, including in space.
In this case, a small CubeSat satellite, appropriately named SpooQy-1, was used to produce pairs of tangled photos using a blue laser diode and nonlinear crystals.
The quantum entanglement instrument. (Center for Quantum Technologies, National University of Singapore)
“In the future, our system could be part of a global quantum network that transmits quantum signals to receivers on Earth or to other spacecraft,” says quantum physicist Aitor Villar of the National University of Singapore.
“These signals could be used to implement any type of quantum communication application, from quantum key distribution for extremely secure data transmission to quantum teleportation, where information is transferred by replicating the state of a quantum system remotely.”
The achievement is impressive on several levels: Not only did it happen in real space, but it was performed on a computer less than 20 cm by 10 cm (7.87 inches by 3.94 inches) and weighing less than 2, 6 kilograms (5.73 pounds)
(Villar et al., Optics2020)
While the Chinese Micius satellite has the honor of being the first to manage quantum communication from space, SpooQy-1 is smaller. That compactness will be crucial if we are going to use satellites as the basis for future quantum communications.
CubeSat was launched last year from the International Space Station, but was specially designed in a way that protects the tangled photon source from the pressures and temperatures of a launch from Earth, and an orbit around it.
Onboard photon pairs were entangled at temperatures between 16 degrees and 21.5 degrees Celsius (60.8 degrees and 70.07 degrees Fahrenheit).
Not only that, but the system was designed to operate while using as little power as possible. The size, robustness, and low power consumption of SpooQy-1 are remarkable to researchers exploring whether a satellite-based quantum internet could be possible.
Quantum communication with the satellite has not yet been attempted, but this lays the groundwork for it. Scientists are looking for alternative ways to transmit quantum encoded information, because it does not work with standard fiber optics over longer distances.
In the coming years, the team hopes to work on a quantum receiver that can communicate with a CubeSat satellite like this one, and improve the overall ability of CubeSat devices to support quantum networks.
“Progress towards a global space-based quantum network is happening at a rapid rate,” says Villar. “We hope that our work will inspire the next wave of space-based quantum technology missions and that new applications and technologies can benefit from our experimental findings.”
The research has been published in Optics.
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