New receiver means safer data encryption

In the run up to Christmas and the aftermath that is January sales many of us were frantically online shopping, hoping to get that last-minute gift delivered on time or grab a bargain. Yet each time we plug our credit card details into that little box on the screen we put our faith into the complicated computer mathematics and code, either not thinking about it much at all or crossing fingers our data won’t be hacked.

A new generation of encryption codes is being used by anyone who needs to protect our information, from e-commerce sites to health insurance databases or digital voting systems. Going beyond that complicated mathematics, it looks to the fundamental building blocks of our universe – the quantum realm. Supposedly unhackable, these quantum encryption keys offer the ultimate in data security. Using tiny packets of light, called photons, to generate the encryption key means mathematics is useless to break the code.

Eventually, this data has to be decrypted by those who need to read it. This is made possible using telescopes at ground stations on Earth. These fast tracking telescopes are required to receive the data from satellites orbiting our planet, and make sense of it but currently they don’t work well with the satellites – meaning they are unreliable, the data has large margins of error and the photons holding the encryption keys don’t reach the detectors in a reliable way.

A new activity, funded by the GSTP programme and conducted by the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna in collaboration with the Chinese Academy of Science (CAS), has developed a general purpose receiver that can be attached to a telescope to improve its ability to receive the photons and reduce the errors.

The aim of the activity was to launch a Low Earth Orbit satellite purely for quantum science and use it to send data encrypted using the quantum technique between ground stations in Europe and China. IQOQI had already shown that the ground station in Tenerife is capable of receiving entangled photons, but the Chinese satellite was going to be launched into a low-earth orbit (LEO) and the feasibility of tracking such a satellite with the required accuracy needed further investigation. To match the transmitted and received photons, the local time at the satellite and the ground station had to be precisely synchronised, so the team also used a green beacon laser in parallel to their quantum signal to match the two in time.

Using the Ground Station telescope in Tenerife, the receiver the team built was proven to be fully functional. Reliable quantum signals were received from the satellite and they were able to dynamically adjust the ground station receiver to precisely track and maintain a link with the satellite for the entire time it passed overhead.

Next, the team need to assess how they can reduce the background noise of the signal they received before the receiver can be distributed more widely, but this is a first step in making quantum encryption keys a globally used security device and providing better protection for data worldwide.