Quantum-encrypted message sent wirelessly in a city for the first time

24 Aug 2017

Image: pisaphotography/Shutterstock

Researchers have sent a quantum-encrypted message over the air for the first time, which is good news for global IoT networks.

As we edge closer to a new age of connectivity as part of the internet of things (IoT), security researchers are delving into the weird and wonderful world of quantum encryption.

When a message is sent using quantum encryption, photons are encoded with information in the form of quantum bits (qubits) – code that can be a one, zero, or both at the same time.

By using quantum encryption, the possibility is open to create vast, unhackable networks that would prevent major breaches and incidents, such as the WannaCry and Mirai attacks that took place over the past year.

To that end, a team of international researchers has revealed that, for the first time, a quantum-secured message containing more than one bit of information per photon was sent through the air above the city of Ottawa.

Publishing its findings in the journal Optica, Ebrahim Karimi and his team demonstrated wireless, 4D quantum encryption between two buildings over a distance of 300 metres.

What made this breakthrough even more remarkable is that many of Karimi’s peers doubted his team’s chances of being able to transmit a message across a city, with the belief that air turbulence would distort the optical signal.

With some wooden boxes for protection on the roofs of two buildings, the transmitters had an error rate of only 11pc, putting it below the 19pc threshold for secure connection.

Huge potential

Until now, quantum encryption had remained restricted to physical cables, with a Chinese team demonstrating last year that it was capable of sending a quantum-encrypted message at a distance of 400km.

“Our work is the first to send messages in a secure manner using high-dimensional quantum encryption in realistic city conditions, including turbulence,” Karimi said of the breakthrough, which offers greater potential in a wireless world.

“The secure, free-space communication scheme we demonstrated could potentially link Earth with satellites, securely connect places where it is too expensive to install fibre, or be used for encrypted communication with a moving object, such as an aeroplane.”

In addition to making modern telecommunications far more secure, quantum encryption will be deemed a necessity as quantum computing and its seemingly endless potential sees it move out of labs and into the wider world.

In the meantime, the researchers’ next goal is to transmit a message over a distance of 3km, as this is roughly equal to sending the signal through the Earth’s atmosphere to a satellite.

Researcher Alicia Sit, one of those involved in the project, said: “Our long-term goal is to implement a quantum communication network with multiple links, but using more than four dimensions while trying to get around the turbulence.”

Colm Gorey was a senior journalist with Silicon Republic