China research team smashes quantum cryptography record

7 Nov 2016

Lock surrounded by chains. Image: Ruslan Grumble/Shutterstock

A team of researchers from China – with assistance from a lab in the US – has smashed the current quantum cryptography record, by sending a message across a distance of 404km that is impossible to eavesdrop on.

While still in its infancy in comparison with other encryption technologies, an internet based on quantum cryptography – that uses the unusual science of quantum entanglement – would allow two parties to send messages to one another without any possibility of being eavesdropped on.

In its current state, however, the ability to achieve quantum cryptography over global distances has been challenged, with claims that it is simply not feasible in quantum key distribution (QKD) systems.

Doubling previous record

QKD systems are based on a form of cryptography referred to as one-time pad (OTP) that ensures a mathematically unbreakable encryption, permitting that one or both of the keys on either end are not compromised themselves.

Yet now, according to, a team of researchers led by the University of Science and Technology of China has smashed a previous quantum cryptography record, offering hope for bringing the technology into the real world.

Having teamed up with other Chinese research labs and a lab in the US, the team revealed that using its protocol, dubbed measurement-device-independent quantum key distribution (MDIQKD), it sent a secure message over a distance of 404km.

By doubling the previous record, the team’s findings published in Physical Review Letters suggests that an internet protected by quantum cryptography is now a real possibility in the years to come.

500-fold increase in speed

Four years in the making, MDIQKD broke the distance record by sending infrared photons across lengths of optical fibres, just shy of the distance between Cork and Belfast.

What makes it particularly capable as a secure method of communication is that it can use ‘decoy’ photons during the transmission process to detect when eavesdropping on a third party occurs.

Another major breakthrough achieved by the research team was with its speed, as it noted a 500-fold increase compared with past methods.

One previous quantum cryptography method was only able to achieve a data transfer speed of 0.018bps across a distance of 200km, but this recent attempt achieved a speed of 1.38kbps at the 102km mark.

China seeking solace in quantum

This speed would be significant enough to allow a phone conversation completely secured by quantum cryptography.

Last September, a team from the University of Calgary in Canada and researchers in the US made a breakthrough in teleporting a light particle across a distance of 6km. This was part of research into the development of quantum internet and by proxy, quantum encryption.

Fearing the influence of external superpowers on accessing state secrets and the information of its citizens, China has been investing heavily in quantum encryption technology. This was most recently seen in the launch of a test bed ‘hack-proof’ quantum satellite last August.

Colm Gorey was a senior journalist with Silicon Republic