What is... Quantum internet?

We have quantum computers, quantum security and quantum leaps – well, maybe the latter’s only on TV. Here’s what happens when qubits get networked

Experts hope to use qubits to send unhackable information

Quantum is the new next-gen buzzword for computing, promising hyper-fast processing power that could take out existing encryption. But what happens if you apply the same quantum ideas to network communications? That’s the idea behind quantum internet: using the physics of qubits – quantum bits – to send and receive information, in a near-perfectly secure way.

What is a quantum internet? Rather than use radio frequencies to send information, a quantum internet would use quantum signals. At the core of quantum physics is entanglement – fiddle with this bit here and it affects one elsewhere – and teleportation, which uses that connection to send information. The state of a particle is transferred to the second particle, erasing the state in the first. Nothing physical is being teleported, but it looks as though it has. If you think your broadband is fast now, quantum communications happen instantly.

Would we even need a network? The information may be “teleporting”, but you need to link up your photons to get them entangled first. For that, photons are sent along the network to connect with those that are communicating. However, they don’t like to travel as far as we’d like.

What’s holding this back? Quantum communications have been held back by distance, as the photons can’t travel further than a few tens of kilometres down an optical line without having issues. And you can’t simply send copies and hope one gets there – that’s contrary to quantum physics, which means you can’t make identical copies. Solutions abound, such as quantum repeaters and nodes to link up shorter lengths of fibre, but working out the kinks will take time. There are other challenges, notably that when the information arrives down a quantum internet line, we’re not very good at storing it, so we need to figure out the best material for quantum memory.

Is anyone building one? Academics are battling to see who can create the first quantum internet. The University of Delft has plans to link four cities in the Netherlands by 2020, while there’s a quantum network linking Beijing and Shanghai, although it relies on nodes to cover the distance. The researchers behind the Chinese network believe a global quantum network could exist by 2030, and they’ve managed transmissions over 1,200km via a quantum satellite, sending information from ground level to space using entangled photons. But other academics aren’t holding their breath that we’ll have a large quantum network in our lifetimes.

Quantum for everyone! There’s no reason to stop using your existing network. Instead, a quantum internet would be ideal for secure communications. The message and encryption key can be sent separately so it’s obvious if anyone meddles with either, creating an essentially unhackable network.