US military wants to secure the internet by making it more quantum

The US military has launched an initiative to determine how quantum devices and particles could augment traditional communication networks – like those that make up the internet – to make them more secure.

Quantum networks that share information via particles’ quantum states are extremely secure. For instance, the messages these states carry cannot be surreptitiously copied, thanks to the properties of quantum physics. Because of this, several quantum communication networks have already been built around the world.

But a fully quantum internet has been hindered because we don’t know how to build some of the devices crucial for making it work. Instead of waiting for all of the outstanding questions to be answered, the US Defense Advanced Research Projects Agency (DARPA) has started a programme to identify the near-term benefits of making existing communication networks more quantum.

Above all, the agency’s aim is to identify quantum additions that will be practical and useful in the near future, says Allyson O’Brien, programme manager for DARPA’s Quantum-Augmented Network (QuANET) programme. “We can’t make everything quantum off the bat,” she says.

In August, the QuANET team came together for a hackathon that culminated in a concrete demonstration: light put into a special quantum state was used to transmit images such as the DARPA logo and a simple graphic of a cat. At its best, this early test of a quantum-augmented network achieved bit rates high enough to stream high-definition video.

O’Brien says the quantum states from this demonstration are just one example of a range of quantumness that the QuANET programme is exploring. Researchers are also working on “hyperentanglement”, where several properties of light would be simultaneously linked through the inextricable bond of quantum entanglement. Preliminary mathematical models suggest hyperentanglement can help encode more secure information into fewer light signals, cutting down on the resources the quantum network would need.

On the other end of the spectrum, the team is exploring making light in their network not fully quantum but quantum-like. This involves endowing the light with some properties of quantum states without forcing a full fundamental change in its physical character.

QuANET researchers are also developing a quantum network interface card, a component that can be plugged into communication devices to allow them to transmit and receive quantum signals.

There are many open questions about how useful these interventions might be, and at what stages and levels of network design they are best deployed. But O’Brien says QuANET is bringing together quantum physicists, electrical engineers and network specialists to answer these questions as realistically as possible.

“Quantum networks are not going to solve everything,” says Joseph Lukens at Purdue University in Indiana. They only excel at some tasks, and the most efficient way to run them will still include some traditional networking devices. “The future is that quantum networks will automatically have to be integrated with classical networks,” says Lukens. In his view, this makes programmes like QuANET valuable – despite all the questions about how to quantumly augment the very well-developed and ubiquitous internet infrastructure we already have.

It would be a great success if the programme developed a system where users could sometimes switch to an ultra-secure “quantum mode” on their devices. That way, we could all take advantage of these augmentations without having to know anything about the laws of quantum physics, says Lukens.