Quantum physics experiment

Quantum breakthrough enables totally secure internet communications

Image credit: University of Bristol/ÖAW-Klaus Pichler

A quantum network has been developed that enables people to send “totally secure” messages over the internet that cannot be intercepted by hackers.

Led by the University of Bristol, the quantum breakthrough has the potential to serve millions of users and is understood to be the largest-ever quantum network of its kind.

By deploying a new technique, harnessing the simple laws of physics, it can make messages completely safe from interception while also overcoming major challenges which have previously limited advances in the much-hyped quantum sector.

The team’s quantum technique applies a principle called entanglement, which Albert Einstein described as ‘spooky action at a distance.’

It exploits the power of two different particles placed in separate locations, potentially thousands of miles apart, to simultaneously mimic each other. This process presents far greater opportunities for quantum computers, sensors, and information processing.

So far physicists have developed a form of secure encryption, known as quantum key distribution, in which particles of light, called photons, are transmitted. The process allows two parties to share, without risk of interception, a secret key used to encrypt and decrypt information. But to date this technique has only been effective between two users.

“Instead of having to replicate the whole communication system, this latest methodology, called multiplexing, splits the light particles, emitted by a single system, so they can be received by multiple users efficiently,” lead author Dr Siddarth Joshi said.

The team created a network for eight users using just eight receiver boxes, whereas the former method would need the number of users multiplied many times - in this case, amounting to 56 boxes. As the user numbers grow, the logistics become increasingly unviable - for instance 100 users would take 9,900 receiver boxes.

To demonstrate its functionality across distance, the receiver boxes were connected to optical fibres via different locations across Bristol and the ability to transmit messages via quantum communication was tested using the city’s existing optical fibre network.

Whereas previous quantum systems have taken years to build, at a cost of millions or even billions of pounds, this network was created within months for less than £300,000. The financial advantages grow as the network expands, so while 100 users on previous quantum systems might cost in the region of £5bn, Dr Joshi believes multiplexing technology could slash that to around £4.5m, less than 1 per cent.

“This represents a massive breakthrough and makes the quantum internet a much more realistic proposition,” Dr Joshi said. “Until now, building a quantum network has entailed huge cost, time, and resource, as well as often compromising on its security which defeats the whole purpose.”

“Our solution is scalable, relatively cheap and, most important of all, impregnable. That means it’s an exciting game changer and paves the way for much more rapid development and widespread rollout of this technology.”

While commercialisation of quantum systems are probably still some way off, a number of breakthroughs have occurred in recent years such as last month’s demonstration of a quantum system that can be sustained for 10,000 times longer than what was previously possible.

In April, another team demonstrated a quantum processor that could operate in the highest temperatures yet.

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